feat(packaging/arch): split package — add punktfunk-client for the Deck

The Decky plugin (b3f98a5) launches `punktfunk-client`, but the Arch package only
shipped the host, so the Deck had nothing to launch. Convert the PKGBUILD to a
split package (pkgbase=punktfunk → punktfunk-host + punktfunk-client), mirroring the
rpm subpackages and the two deb build scripts:

- punktfunk-host: unchanged artifact set + NVENC/compositor optdepends.
- punktfunk-client: the GTK4 binary + io.unom.Punktfunk.desktop + the hidraw udev
  rule + the 32MB recv-buffer sysctl; depends gtk4/libadwaita/sdl3/ffmpeg/pipewire/
  opus; optdepends libva-mesa-driver (VAAPI decode on the Deck's AMD APU, software
  fallback otherwise). New punktfunk-client.install scriptlet.
- build-sysext.sh now derives the package name from the file, so it wraps either the
  host OR the client into a systemd-sysext .raw — on a Deck you wrap the client.
- README: split-package usage + a "Steam Deck (the client)" section tying the sysext
  to the Decky plugin (client is on PATH → plugin launches `punktfunk-client
  --connect host:port`). Clarified the VAAPI gap is host-ENCODE only; the client
  DECODES via VAAPI on the Deck today, so streaming to a Deck works now.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

packaging/arch/PKGBUILD

@@ -1,87 +1,75 @@
 # Maintainer: unom <noreply@anthropic.com>
 #
-# Arch Linux / SteamOS package for the punktfunk streaming HOST. Mirrors the artifact
-# set of packaging/rpm/punktfunk.spec and packaging/debian/build-deb.sh exactly.
+# Arch Linux / SteamOS split package: punktfunk-host (the gaming-rig HOST, NVENC) and
+# punktfunk-client (the GTK4 couch/Deck CLIENT). Mirrors the rpm subpackages
+# (packaging/rpm/punktfunk.spec) and the two deb build scripts. On a Steam Deck you want
+# `punktfunk-client` (it's what the Decky plugin launches); on a gaming rig, `punktfunk-host`.
 #
 # Two build modes:
 #   - AUR / standalone:  makepkg in this dir (fetches the git tag below).
 #   - In-tree / CI:       PF_SRCDIR=$(git rev-parse --show-toplevel) makepkg --holdver
 #                         (builds the working tree instead of the tagged source — see build()).
 #
-# IMPORTANT: encode is NVENC-only (crates/punktfunk-host/src/encode/linux.rs). This package is
-# functional on NVIDIA hosts (nvidia-utils + Arch's NVENC-enabled ffmpeg). On an AMD Steam Deck
-# it installs but CANNOT encode until a VAAPI (hevc_vaapi) backend exists — see packaging/arch/README.md.
-pkgname=punktfunk-host
+# IMPORTANT: host encode is NVENC-only (crates/punktfunk-host/src/encode/linux.rs) — functional on
+# NVIDIA hosts; an AMD Deck-as-HOST needs a VAAPI backend first. The CLIENT decodes via VAAPI
+# (AMD/Intel, incl. the Deck) with a software fallback, so it works everywhere. See README.md.
+pkgbase=punktfunk
+pkgname=('punktfunk-host' 'punktfunk-client')
 pkgver=0.0.1
 pkgrel=1
-pkgdesc="Low-latency desktop/game streaming host (Moonlight-compatible + punktfunk/1)"
 arch=('x86_64')
 url="https://git.unom.io/unom/punktfunk"
 license=('MIT OR Apache-2.0')
 
-# Runtime libs the binary links or drives. NVENC + GPU EGL/CUDA come from the NVIDIA driver
-# (nvidia-utils) — kept an optdepend, never a hard dep, exactly as the RPM (__requires_exclude
-# libcuda) and deb (shlibdeps grep-filter) do: the driver is installed out of band.
-depends=(
-  'ffmpeg'          # libavcodec/format/util — Arch's ffmpeg ships hevc_nvenc/av1_nvenc
-  'pipewire'        # capture + audio transport
-  'pipewire-pulse'  # desktop audio bridge
-  'wireplumber'     # PipeWire session manager
-  'opus'            # GameStream/punktfunk Opus audio
-  'libei'           # input injection (RemoteDesktop portal / EIS)
-  'mesa'            # libgbm (+ EGL on non-NVIDIA)
-  'libglvnd'        # libGL/libEGL loader
-  'libxkbcommon'    # virtual keyboard keymap
-  'wayland'         # wayland-client (vdisplay backends)
-)
-optdepends=(
-  'nvidia-utils: NVENC hardware encode + GPU EGL/CUDA zero-copy (REQUIRED to encode on NVIDIA)'
-  'gamescope: per-session nested compositor backend (no desktop login needed) — needs >=3.16.22'
-  'kwin: stream a KDE Plasma desktop (kwin VirtualDisplay backend)'
-  'mutter: stream a GNOME desktop (Mutter RecordVirtual backend)'
-  'sway: stream a wlroots desktop (Sway VirtualDisplay backend)'
-  'xdg-desktop-portal-kde: portal for the headless KDE session helper'
-  'xdg-desktop-portal-wlr: portal for the headless Sway session helper'
-)
-makedepends=('rust' 'cargo' 'clang' 'cmake' 'nasm' 'pkgconf' 'git')
+# All build deps for both crates (Arch runtime packages ship their own headers, so these cover
+# build + link). aws-lc/ring need clang+cmake; nasm is for asm.
+makedepends=('rust' 'cargo' 'clang' 'cmake' 'nasm' 'pkgconf' 'git'
+             'gtk4' 'libadwaita' 'sdl3' 'ffmpeg' 'pipewire' 'wayland' 'libxkbcommon' 'opus' 'libei')
 
 # AUR source (a tagged release). For an in-tree CI build, set PF_SRCDIR to the repo root and
 # build() uses it instead; see the README.
 source=("git+https://git.unom.io/unom/punktfunk.git#tag=v${pkgver}")
 sha256sums=('SKIP')
-install="${pkgname}.install"
 
 _repo() { printf '%s' "${PF_SRCDIR:-$srcdir/punktfunk}"; }
 
 build() {
   cd "$(_repo)"
   export RUSTUP_TOOLCHAIN=stable CARGO_TARGET_DIR="$srcdir/target"
-  # The zero-copy FFI link-needs libcuda at build time; nvidia-utils provides it on an NVIDIA
-  # builder. On a GPU-less builder, symlink the CUDA stub into the link path first (same caveat
-  # the RPM documents): ln -s "$(find / -name libcuda.so -path '*stubs*' | head -1)" /usr/lib/
-  cargo build --release --locked -p punktfunk-host
+  # The host's zero-copy FFI link-needs libcuda at build time; nvidia-utils provides it on an
+  # NVIDIA builder. On a GPU-less builder symlink the CUDA stub into the link path first (same
+  # caveat the RPM documents): ln -s "$(find / -name libcuda.so -path '*stubs*'|head -1)" /usr/lib/
+  cargo build --release --locked -p punktfunk-host -p punktfunk-client-linux
 }
 
-package() {
+package_punktfunk-host() {
+  pkgdesc="Low-latency desktop/game streaming HOST (Moonlight-compatible + punktfunk/1)"
+  # NVENC + GPU EGL/CUDA come from the NVIDIA driver (nvidia-utils) — kept an optdepend, never a
+  # hard dep, exactly as the RPM (__requires_exclude libcuda) and deb (shlibdeps filter) do.
+  depends=('ffmpeg' 'pipewire' 'pipewire-pulse' 'wireplumber' 'opus' 'libei'
+           'mesa' 'libglvnd' 'libxkbcommon' 'wayland')
+  optdepends=('nvidia-utils: NVENC hardware encode + GPU EGL/CUDA zero-copy (REQUIRED to encode on NVIDIA)'
+              'gamescope: per-session nested compositor backend (no desktop login needed) — needs >=3.16.22'
+              'kwin: stream a KDE Plasma desktop (kwin VirtualDisplay backend)'
+              'mutter: stream a GNOME desktop (Mutter RecordVirtual backend)'
+              'sway: stream a wlroots desktop (Sway VirtualDisplay backend)'
+              'xdg-desktop-portal-kde: portal for the headless KDE session helper'
+              'xdg-desktop-portal-wlr: portal for the headless Sway session helper')
+  install=punktfunk-host.install
   local R; R="$(_repo)"; local T="$srcdir/target/release"
 
   install -Dm0755 "$T/punktfunk-host"                 "$pkgdir/usr/bin/punktfunk-host"
-
   # /dev/uinput + /dev/uhid -> input group (virtual gamepads + DualSense UHID)
   install -Dm0644 "$R/scripts/60-punktfunk.rules"     "$pkgdir/usr/lib/udev/rules.d/60-punktfunk.rules"
   # 32 MB UDP socket buffers (send-side headroom at high bitrate)
   install -Dm0644 "$R/scripts/99-punktfunk-net.conf"  "$pkgdir/usr/lib/sysctl.d/99-punktfunk-net.conf"
-
-  # systemd USER units (the host runs in the graphical session, not as root); the source units
-  # point at the dev tree — repoint ExecStart at the installed paths (mirrors rpm/deb).
+  # systemd USER units (the host runs in the graphical session, not as root); repoint ExecStart.
   install -Dm0644 "$R/scripts/punktfunk-host.service" "$pkgdir/usr/lib/systemd/user/punktfunk-host.service"
   sed -i 's#%h/punktfunk/target/release/punktfunk-host#/usr/bin/punktfunk-host#' \
     "$pkgdir/usr/lib/systemd/user/punktfunk-host.service"
-  install -Dm0644 "$R/scripts/punktfunk-kde-session.service" "$pkgdir/usr/lib/systemd/user/punktfunk-kde-session.service" 2>/dev/null || true
-  [ -f "$pkgdir/usr/lib/systemd/user/punktfunk-kde-session.service" ] && \
-    sed -i 's#%h/punktfunk/scripts/headless/run-headless-kde.sh#/usr/share/punktfunk/headless/run-headless-kde.sh#' \
-      "$pkgdir/usr/lib/systemd/user/punktfunk-kde-session.service"
-
+  install -Dm0644 "$R/scripts/punktfunk-kde-session.service" "$pkgdir/usr/lib/systemd/user/punktfunk-kde-session.service"
+  sed -i 's#%h/punktfunk/scripts/headless/run-headless-kde.sh#/usr/share/punktfunk/headless/run-headless-kde.sh#' \
+    "$pkgdir/usr/lib/systemd/user/punktfunk-kde-session.service"
   # headless session helpers + env templates + OpenAPI doc
   install -Dm0755 "$R/scripts/headless/run-headless-kde.sh"  "$pkgdir/usr/share/punktfunk/headless/run-headless-kde.sh"
   install -Dm0755 "$R/scripts/headless/run-headless-sway.sh" "$pkgdir/usr/share/punktfunk/headless/run-headless-sway.sh"
@@ -91,8 +79,31 @@ package() {
   install -Dm0644 "$R/packaging/bazzite/host.env"            "$pkgdir/usr/share/punktfunk/host.env.bazzite"
   install -Dm0644 "$R/packaging/kde/host.env"                "$pkgdir/usr/share/punktfunk/host.env.kde"
   install -Dm0644 "$R/docs/api/openapi.json"                 "$pkgdir/usr/share/punktfunk/openapi.json"
-
-  install -Dm0644 "$R/LICENSE-MIT"    "$pkgdir/usr/share/licenses/$pkgname/LICENSE-MIT"
-  install -Dm0644 "$R/LICENSE-APACHE" "$pkgdir/usr/share/licenses/$pkgname/LICENSE-APACHE"
-  install -Dm0644 "$R/README.md"      "$pkgdir/usr/share/doc/$pkgname/README.md"
+  install -Dm0644 "$R/LICENSE-MIT"    "$pkgdir/usr/share/licenses/punktfunk-host/LICENSE-MIT"
+  install -Dm0644 "$R/LICENSE-APACHE" "$pkgdir/usr/share/licenses/punktfunk-host/LICENSE-APACHE"
+  install -Dm0644 "$R/README.md"      "$pkgdir/usr/share/doc/punktfunk-host/README.md"
+}
+
+package_punktfunk-client() {
+  pkgdesc="Low-latency desktop/game streaming CLIENT (GTK4) — the couch/Deck side"
+  # The GTK4/libadwaita client: SDL3 gamepads, FFmpeg (VAAPI) decode, PipeWire audio/mic.
+  depends=('gtk4' 'libadwaita' 'sdl3' 'ffmpeg' 'pipewire' 'wireplumber' 'pipewire-pulse'
+           'opus' 'libglvnd')
+  optdepends=('libva-mesa-driver: VAAPI hardware decode on AMD (incl. Steam Deck); software fallback otherwise'
+              'intel-media-driver: VAAPI hardware decode on Intel'
+              'gamescope: run the client fullscreen in a Gaming-Mode session')
+  install=punktfunk-client.install
+  local R; R="$(_repo)"; local T="$srcdir/target/release"
+
+  install -Dm0755 "$T/punktfunk-client" "$pkgdir/usr/bin/punktfunk-client"
+  install -Dm0644 "$R/packaging/linux/io.unom.Punktfunk.desktop" \
+    "$pkgdir/usr/share/applications/io.unom.Punktfunk.desktop"
+  # DualSense hidraw access (full pad fidelity through SDL's HIDAPI driver).
+  install -Dm0644 "$R/scripts/70-punktfunk-client.rules" \
+    "$pkgdir/usr/lib/udev/rules.d/70-punktfunk-client.rules"
+  # 32 MB UDP recv buffer (so high-bitrate streams don't overflow the kernel socket buffer).
+  install -Dm0644 "$R/scripts/99-punktfunk-client-net.conf" \
+    "$pkgdir/usr/lib/sysctl.d/99-punktfunk-client-net.conf"
+  install -Dm0644 "$R/LICENSE-MIT"    "$pkgdir/usr/share/licenses/punktfunk-client/LICENSE-MIT"
+  install -Dm0644 "$R/LICENSE-APACHE" "$pkgdir/usr/share/licenses/punktfunk-client/LICENSE-APACHE"
 }

packaging/arch/README.md

@@ -1,15 +1,18 @@
 # punktfunk on Arch Linux / SteamOS
 
-Packaging for the punktfunk streaming **host** on Arch and Arch-derived immutable distros
-(SteamOS 3, etc.). Mirrors the artifact set of `packaging/rpm/punktfunk.spec` and
-`packaging/debian/build-deb.sh`.
+Packaging for punktfunk on Arch and Arch-derived immutable distros (SteamOS 3, etc.). The
+`PKGBUILD` is a **split package** producing both **`punktfunk-host`** (the gaming-rig host) and
+**`punktfunk-client`** (the GTK4 couch/Deck client) — mirrors the rpm subpackages
+(`packaging/rpm/punktfunk.spec`) and the two deb build scripts. On a **Steam Deck you want
+`punktfunk-client`** (it's what the [Decky plugin](../../clients/decky/) launches); on a gaming
+rig, `punktfunk-host`.
 
-> ⚠️ **Encode is NVENC-only today.** `crates/punktfunk-host/src/encode/linux.rs` implements
-> `hevc_nvenc`/`av1_nvenc`/`h264_nvenc` and a CUDA zero-copy path — there is **no VAAPI backend**.
-> So this package is functional on **Arch + NVIDIA** (the realistic target). On an **AMD Steam
-> Deck it installs but cannot encode** until a `hevc_vaapi`/`av1_vaapi` encoder is added in
-> `src/encode/` — a code change, not a packaging one. (`bazzite-deck-nvidia`, i.e. SteamOS-style
-> images running on NVIDIA hardware, work fine — they're NVIDIA.)
+> ⚠️ **Host encode is NVENC-only today.** `crates/punktfunk-host/src/encode/linux.rs` implements
+> `hevc_nvenc`/`av1_nvenc`/`h264_nvenc` + a CUDA zero-copy path — there is **no VAAPI encoder**. So
+> `punktfunk-host` works on **Arch + NVIDIA** (incl. `bazzite-deck-nvidia`); an **AMD Deck-as-host**
+> can't encode until a `hevc_vaapi` backend is added (a code change, not packaging). The **client
+> is unaffected** — `punktfunk-client` decodes via **VAAPI on AMD/Intel** (the Deck) with a software
+> fallback, so streaming *to* a Deck works today.
 
 ## Arch Linux (mutable)
 
@@ -64,7 +67,28 @@ systemctl --user enable --now punktfunk-host     # the user unit is now under /u
 The udev rule, sysctl, and systemd **user** unit all live under `/usr/lib`, so the merged sysext
 exposes them. `systemd-sysext refresh` re-merges after a reboot.
 
+## Steam Deck — the client (what the Decky plugin launches)
+
+To stream *to* a Deck, you install **`punktfunk-client`** there — same sysext mechanism, but
+wrapping the client package instead. The split `makepkg` produces both `.pkg.tar.zst` files; on the
+Deck use the client one:
+```sh
+cd packaging/arch && PF_SRCDIR="$(git rev-parse --show-toplevel)" makepkg -f --holdver
+bash build-sysext.sh punktfunk-client-*.pkg.tar.zst        # → punktfunk-client.raw
+# on the Deck:
+sudo cp punktfunk-client.raw /var/lib/extensions/
+sudo systemctl enable --now systemd-sysext
+sudo pacman -S --needed libva-mesa-driver                  # VAAPI hw decode on the Deck's AMD APU
+```
+Now `punktfunk-client` is on `PATH`, so the **[Decky plugin](../../clients/decky/)** finds and
+launches it (`punktfunk-client --connect host:port`) — gamescope composites its video like a game.
+The client needs no `/dev/uinput` or compositor-spawning rights (it captures input and decodes),
+so it's a much lighter sysext than the host.
+
 ## Files
-- `PKGBUILD` — the package recipe (builds the working tree via `PF_SRCDIR`, or a git tag for AUR).
-- `punktfunk-host.install` — pacman scriptlet (udev reload + sysctl + first-run hint), mirrors RPM `%post`.
-- `build-sysext.sh` — wraps a built `.pkg.tar.zst` into a `systemd-sysext` `.raw` for SteamOS.
+- `PKGBUILD` — split package: `punktfunk-host` + `punktfunk-client` (builds the working tree via
+  `PF_SRCDIR`, or a git tag for AUR).
+- `punktfunk-host.install` / `punktfunk-client.install` — pacman scriptlets (udev reload + sysctl +
+  first-run hint), mirror the RPM `%post` / deb postinst.
+- `build-sysext.sh` — wraps either built `.pkg.tar.zst` into a `systemd-sysext` `.raw` for SteamOS
+  (derives the name from the package, so it works for host or client).

packaging/arch/build-sysext.sh

@@ -1,16 +1,19 @@
 #!/usr/bin/env bash
-# Wrap a built punktfunk-host pacman package into a systemd-sysext image — the update-survivable
-# way to add the host to an immutable Arch-derived distro (SteamOS 3): the .raw overlays /usr
-# read-only from the writable /var/lib/extensions/, so it persists across A/B OS updates with no
-# `steamos-readonly disable`. Needs `bsdtar`/`tar`, `squashfs-tools` (mksquashfs).
+# Wrap a built punktfunk pacman package into a systemd-sysext image — the update-survivable way to
+# add it to an immutable Arch-derived distro (SteamOS 3): the .raw overlays /usr read-only from the
+# writable /var/lib/extensions/, so it persists across A/B OS updates with no `steamos-readonly
+# disable`. Works for either split package — on a Steam Deck you'd wrap the CLIENT. Needs
+# `bsdtar`/`tar`, `squashfs-tools` (mksquashfs).
 #
-# Usage:  bash build-sysext.sh <punktfunk-host-*.pkg.tar.zst>
-# Output: punktfunk-host.raw
+# Usage:  bash build-sysext.sh <punktfunk-{host,client}-*.pkg.tar.zst>
+# Output: <pkgname>.raw   (e.g. punktfunk-client.raw)
 set -euo pipefail
 
-PKG="${1:?usage: build-sysext.sh <punktfunk-host-*.pkg.tar.zst>}"
+PKG="${1:?usage: build-sysext.sh <punktfunk-{host,client}-*.pkg.tar.zst>}"
 [ -f "$PKG" ] || { echo "no such package: $PKG" >&2; exit 1; }
-NAME=punktfunk-host
+# Derive the package name from the file (pkgname is everything before the -<version>).
+NAME="$(basename "$PKG" | sed -E 's/-[0-9].*//')"
+[ -n "$NAME" ] || { echo "could not derive package name from $PKG" >&2; exit 1; }
 
 STAGE="$(mktemp -d)"
 trap 'rm -rf "$STAGE"' EXIT
@@ -36,4 +39,8 @@ rm -f "$OUT"
 mksquashfs "$STAGE" "$OUT" -all-root -noappend -quiet
 echo "built $OUT"
 echo "  install:  sudo cp $OUT /var/lib/extensions/ && sudo systemctl enable --now systemd-sysext"
-echo "  then:     systemctl --user enable --now $NAME"
+if [ "$NAME" = "punktfunk-host" ]; then
+  echo "  then:     systemctl --user enable --now punktfunk-host"
+else
+  echo "  then:     run 'punktfunk-client' (or let the Decky plugin launch it)"
+fi

packaging/arch/punktfunk-client.install

@@ -0,0 +1,19 @@
+# pacman scriptlet for the GTK4 client — mirrors build-client-deb.sh's postinst.
+post_install() {
+  udevadm control --reload-rules 2>/dev/null || true
+  udevadm trigger --subsystem-match=hidraw 2>/dev/null || true
+  update-desktop-database /usr/share/applications 2>/dev/null || true
+  # Apply the 32 MB UDP recv-buffer tuning now (also auto-applied at boot by systemd-sysctl).
+  sysctl -p /usr/lib/sysctl.d/99-punktfunk-client-net.conf >/dev/null 2>&1 || true
+  cat <<'MSG'
+punktfunk-client installed.
+  punktfunk-client                         # GUI: discover hosts on the LAN + connect
+  punktfunk-client --connect HOST[:PORT]   # direct / scripted (this is what the Decky plugin runs)
+On a Steam Deck / AMD box, install 'libva-mesa-driver' for hardware (VAAPI) decode.
+MSG
+}
+
+post_upgrade() {
+  udevadm control --reload-rules 2>/dev/null || true
+  sysctl -p /usr/lib/sysctl.d/99-punktfunk-client-net.conf >/dev/null 2>&1 || true
+}