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 b28ddfc (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/arch.md

@@ -58,25 +58,30 @@ tuning, and example configs. Updates later are just `sudo pacman -Syu`.
 
 ## 4. Configure and run
 
-The host runs as a systemd **`--user`** service — it needs your session's PipeWire and D-Bus.
-Copy a starting config, enable the service, and enable linger so it starts at boot without a login:
+The host runs as a systemd **`--user`** service — it needs your session's PipeWire and D-Bus. Copy a
+starting config:
 
 ```sh
 mkdir -p ~/.config/punktfunk
-cp /usr/share/punktfunk/host.env.example ~/.config/punktfunk/host.env   # then edit
+cp /usr/share/punktfunk/host.env.example ~/.config/punktfunk/host.env
+```
+
+How the host creates its virtual display and injects input depends on your desktop, not your distro —
+edit `host.env` for the desktop you run, following its page for the exact settings and any quirks:
+
+- [KDE Plasma (KWin)](/docs/kde)
+- [GNOME (Mutter)](/docs/gnome)
+- [Steam / gamescope](/docs/gamescope)
+- [Sway / wlroots](/docs/sway)
+
+Then enable the service and turn on linger so it starts at boot without a login:
+
+```sh
 systemctl --user daemon-reload
 systemctl --user enable --now punktfunk-host
 sudo loginctl enable-linger "$USER"
 ```
 
-Which compositor the host captures depends on your desktop — it drives a per-client virtual output
-via KWin (Plasma), Mutter (GNOME), or wlroots (Sway), or spawns a headless **gamescope** session
-per connect. For a headless appliance, the package also ships `punktfunk-kde-session.service`
-(a dedicated `kwin --virtual` session, same as the [Fedora KDE](/docs/fedora-kde#3-kwin-streaming-session)
-guide — `cp /usr/share/punktfunk/host.env.kde ~/.config/punktfunk/host.env` and enable it alongside
-the host). See [Configuration](/docs/configuration) for every knob and
-[Running as a Service](/docs/running-as-a-service) for the service model.
-
 Check it came up:
 
 ```sh
@@ -84,27 +89,10 @@ systemctl --user status punktfunk-host          # active
 journalctl --user -u punktfunk-host -f          # watch a client connect
 ```
 
-### Web console
-
-The console (status, paired devices, arm pairing) ships as `punktfunk-web` — enable it, then open
-`http://<host-ip>:47992`:
-
-```sh
-systemctl --user enable --now punktfunk-web
-```
-
-#### Console login password
-
-On first start `punktfunk-web-init` generates a random login password and saves it to
-`~/.config/punktfunk/web-password` (as `PUNKTFUNK_UI_PASSWORD=…`). Read it back at any time:
-
-```sh
-journalctl --user -u punktfunk-web-init | sed -n 's/.*password generated: //p'
-sed -n 's/^PUNKTFUNK_UI_PASSWORD=//p' ~/.config/punktfunk/web-password
-```
-
-To set your own, edit that file and `systemctl --user restart punktfunk-web`. Forgot it? See
-[Forgot your Password?](/docs/forgot-password).
+Enable the browser console, find your login password, and arm PIN pairing from
+[The Web Console](/docs/web-console). For a headless KWin appliance that streams at boot with no
+graphical login, see [KDE → Headless session](/docs/kde#headless-session). Full reference:
+[Configuration](/docs/configuration) · [Running as a Service](/docs/running-as-a-service).
 
 ## 5. Open the firewall (if you have one)
 
@@ -147,9 +135,9 @@ opened. Full port lists (`nftables`, explicit ports) are in
 ## 6. Connect a client
 
 From any [client](/docs/clients), `--discover` finds the host on the LAN. On first connect, complete
-the **PIN pairing** — arm it from the host's web console, which displays a 4-digit PIN to type into
-the client. (Pairing is required by default; pass `serve --open` only if you deliberately want to
-disable it.) See [Clients](/docs/clients) and [Pairing](/docs/pairing).
+the **PIN pairing**: arm it from [The Web Console](/docs/web-console#arm-pairing), which displays a
+4-digit PIN to type into the client. (Pairing is required by default; pass `serve --open` only if
+you deliberately want to disable it.) See [Clients](/docs/clients) for per-platform setup.
 
 ## Appendix — build from source (PKGBUILD)