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/gnome.md

@@ -0,0 +1,96 @@
+---
+title: GNOME (Mutter)
+description: Configure a punktfunk host for GNOME — host.env, the EGL/lock traps, and a headless session.
+---
+
+Configure a host running **GNOME**. The host drives GNOME's Mutter compositor to create a per-client
+virtual display over D-Bus (`RecordVirtual`), zero-copy. This page assumes the host is already
+installed — see [Ubuntu](/docs/ubuntu), [Fedora](/docs/fedora), or [Arch](/docs/arch).
+
+> 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
+
+Write `~/.config/punktfunk/host.env` with the GNOME settings. The host auto-detects the compositor
+from your session, so the explicit `PUNKTFUNK_COMPOSITOR` is belt-and-braces:
+
+```ini
+# ~/.config/punktfunk/host.env
+WAYLAND_DISPLAY=wayland-0
+XDG_CURRENT_DESKTOP=GNOME
+PUNKTFUNK_COMPOSITOR=mutter
+PUNKTFUNK_VIDEO_SOURCE=virtual
+PUNKTFUNK_ZEROCOPY=1
+PUNKTFUNK_INPUT_BACKEND=libei
+```
+
+You must be on a **Wayland** session (not X11), and Mutter must be **≥ 48**. See the
+[Configuration reference](/docs/configuration) for every option.
+
+## The GL/EGL userspace
+
+On NVIDIA, gnome-shell fails to start — or the host logs **"GPU … not supported by EGL"** — when the
+NVIDIA GL/EGL userspace is missing. The base driver package doesn't always pull it in. Install your
+distro's NVIDIA GL/EGL userspace package — on **Ubuntu/Debian** it's `libnvidia-gl-<version>` matching
+your driver; on **Fedora/Arch** it ships with the RPM Fusion / repo driver — then confirm the glvnd
+vendor file exists:
+
+```sh
+ls /usr/share/glvnd/egl_vendor.d/10_nvidia.json    # must exist
+```
+
+Installing the driver itself is covered on your distro's install page
+([Ubuntu](/docs/ubuntu), [Fedora](/docs/fedora), [Arch](/docs/arch)).
+
+## Do not lock the session
+
+A **locked** GNOME session blocks screen capture — the host fails with
+**"Session creation inhibited"**. On an always-on or headless host there's no one to unlock it, so
+disable the lock:
+
+```sh
+gsettings set org.gnome.desktop.screensaver lock-enabled false
+gsettings set org.gnome.desktop.session idle-delay 0
+```
+
+## Start the host
+
+With `host.env` in place, start the host from **inside your GNOME session**:
+
+```sh
+systemctl --user enable --now punktfunk-host
+journalctl --user -u punktfunk-host -f   # watch it come up and print its identity fingerprint
+```
+
+Then bring up [The Web Console](/docs/web-console) to arm pairing and connect a
+[client](/docs/clients). For an always-on box, see the [headless session](#headless-session) below.
+
+## Headless session
+
+To run with no monitor and no login, keep a GNOME Wayland session up at all times and start the host
+without a login. Have GDM auto-login your user:
+
+```ini
+# /etc/gdm3/custom.conf  (Ubuntu)   ·   /etc/gdm/custom.conf  (Fedora)
+[daemon]
+AutomaticLoginEnable = true
+AutomaticLogin = your-user
+```
+
+Disable the lock (see [above](#do-not-lock-the-session)), then enable the host user service and let it
+linger past logout:
+
+```sh
+systemctl --user enable --now punktfunk-host
+sudo loginctl enable-linger "$USER"
+```
+
+Reboot and the host comes up on the auto-login session. Full walkthrough:
+[Running as a Service](/docs/running-as-a-service).
+
+## Troubleshooting
+
+More fixes — black screen, discovery, pairing — in [Troubleshooting](/docs/troubleshooting).
+
+Once the host is up, bring the console up and pair — see [The Web Console](/docs/web-console).