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"
 }