docs: restructure host setup by distro, configuration by compositor

Split the docs' single distro×desktop axis (ubuntu-gnome / ubuntu-kde / fedora-kde) into two,
which deduplicates the shared mechanics and scales to distros that run several desktops (Arch):

- Install the host — per distro/OS (ubuntu, fedora, arch, bazzite, steamos-host, windows-host):
  GPU driver + package + input group, then a canonical "Configure your desktop" funnel.
- Configure your desktop — per compositor (kde, gnome, gamescope, sway): host.env, compositor
  quirks, the headless session, and starting the host.

New shared web-console page (enable · login password · arm pairing) removes the console/password
block that was copy-pasted across all seven host pages. Merged ubuntu-gnome + ubuntu-kde into
ubuntu; renamed fedora-kde to fedora; kept bazzite and steamos-host as dedicated appliance guides
(trimmed of duplication). Moved the KWin headless session, the GNOME EGL/lock traps, and the
gamescope attach/managed model out of the distro pages onto their compositor pages.

Fixed while restructuring: distro-specific paths on kde (kde-desktop-setup.sh is Fedora/Bazzite-only;
the .deb ships host.env.kde under /usr/share/punktfunk-host), the interactive "start the host" step
that was lost in the merge, sway over-claiming Hyprland, and a pre-existing broken anchor in
how-it-works.

Removal of the three old pages was captured by the preceding commit 8ebb614 (a concurrent commit
swept up the staged git-rm); the net docs tree is correct. Fumadocs build + internal link/anchor
check green.

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

docs-site/content/docs/sway.md

@@ -0,0 +1,68 @@
+---
+title: Sway / wlroots
+description: Configure a punktfunk host on a wlroots compositor (Sway, Hyprland).
+---
+
+The wlroots family can host — but **Sway is the only validated path.** The host adds a per-client
+headless output at the client's exact mode and captures it through the xdg-desktop-portal-wlr (xdpw)
+ScreenCast portal, injecting input via the wlroots virtual pointer/keyboard protocols. Hyprland and
+other wlroots compositors are best-effort (see [How it works](#how-it-works) for the caveat).
+
+This is **not a primary target.** It works and is validated live on **sway 1.11** (zero-copy), but it
+sees far less testing than the KDE and GNOME paths — expect rougher edges. If you have a choice,
+[KDE](/docs/kde) or [GNOME](/docs/gnome) are the better-exercised desktops.
+
+This page assumes the package is already installed — see [Arch](/docs/arch), [Ubuntu](/docs/ubuntu),
+or [Fedora](/docs/fedora).
+
+> New here? Read [Security & Safe Use](/docs/security) first — a streaming host is remote control of
+> the machine, so keep it on a trusted LAN or VPN and require pairing.
+
+## host.env
+
+The host auto-detects a wlroots session, so you usually need nothing here. To force the backend, set
+these in `~/.config/punktfunk/host.env`:
+
+```ini
+PUNKTFUNK_COMPOSITOR=wlroots      # aliases: sway, hyprland
+PUNKTFUNK_INPUT_BACKEND=wlr
+PUNKTFUNK_VIDEO_SOURCE=virtual
+PUNKTFUNK_ZEROCOPY=1              # GPU zero-copy capture→encode; auto-falls back to CPU
+```
+
+See [Configuration](/docs/configuration) for the full reference.
+
+## How it works
+
+- **Video** — the host adds a headless output at the client's exact mode with `swaymsg create_output`.
+  This uses Sway's IPC specifically; other wlroots compositors (Hyprland, …) don't expose an
+  equivalent, so virtual-output creation isn't wired up for them yet — Sway is the supported wlroots
+  path today.
+- **Capture** — it captures that output through the **xdg-desktop-portal-wlr (xdpw)** ScreenCast
+  portal. The host writes a managed chooser config so the output pick is automatic — no interactive
+  picker dialog to answer.
+- **Input** — mouse and keyboard are injected via the wlroots **virtual pointer** and **virtual
+  keyboard** protocols.
+
+For how long the virtual output lives, and extend-vs-exclusive topology, see
+[Virtual displays](/docs/virtual-displays).
+
+## Requirements
+
+- A running wlroots session (Sway, Hyprland, …).
+- **xdg-desktop-portal-wlr (xdpw)** installed and running — the host captures through its ScreenCast
+  portal. Without it there is no video.
+
+## Start the host
+
+With the backend selected, start the host from **inside your Sway session**:
+
+```sh
+systemctl --user enable --now punktfunk-host
+journalctl --user -u punktfunk-host -f
+```
+
+## Bring up the console and pair
+
+Enable the web console, read its login password, and arm PIN pairing — see
+[The Web Console](/docs/web-console). Then [connect a client](/docs/clients).