docs(env): stop teaching the compositor pin + uid-1000 anchors in starters

Field triage (Nobara, Discord): the kde.md starter host.env told desktop
users to set PUNKTFUNK_COMPOSITOR=kwin, which PINS the backend — detect()
short-circuits and the capture-loss rebuild never re-detects — so a
mid-stream switch to Game Mode killed the stream instead of following it.
A follow-up hardcoded XDG_RUNTIME_DIR=/run/user/1000 anchor broke PipeWire
for any non-1000 uid (pw audio connect: Creation failed).

Revamp across every starter/example/reference:
- Desktop starters (kde/gnome/hyprland/sway) shrink to
  PUNKTFUNK_VIDEO_SOURCE=virtual + an explicit warning that pinning
  disables session-following; forcing a backend is CI/appliance-only.
- host.env.example: rewritten around auto-detection; anchors demoted to a
  commented ssh/cron-only block with the uid trap spelled out; the
  gamescope ATTACH/MANAGED knobs documented (previously missing);
  case-sensitivity called out.
- packaging/bazzite/host.env + README: drop the uid-1000 anchors (a
  systemctl --user service inherits/derives them); README's stale
  PUNKTFUNK_COMPOSITOR=gamescope-era template synced to the real one.
- packaging/kde/host.env: loud APPLIANCE-ONLY header (it pins on purpose).
- configuration.md: session-anchors section inverted to "leave unset",
  compositor row states the pin consequence, case-sensitivity note.
- troubleshooting.md: new "session fails right after editing host.env"
  section (case, wrong-uid anchors, stale pin, restart-to-apply).
- gamescope.md/bazzite.md: attach/managed descriptions match current
  behavior (managed is the infra-detected default; attach re-modes a
  box-owned session to the client's resolution).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

docs-site/content/docs/gamescope.md

@@ -17,18 +17,20 @@ from the install guide for your OS: [Bazzite](/docs/bazzite) or [SteamOS (Host)]
 
 ## Attach vs managed
 
-There are two mutually-exclusive models for a gamescope box; pick one. The shipped default is
-**attach**.
+There are two mutually-exclusive models for a gamescope box; pick one. With **nothing set**, a box
+that has gamescope session infrastructure (Bazzite, SteamOS, Nobara) gets **managed**; the
+[Bazzite template](/docs/bazzite) ships with **attach** chosen instead.
 
-- **Attach** (`PUNKTFUNK_GAMESCOPE_ATTACH=1`, the default) — the **box** owns its gamescope session
-  and decides Gaming vs Desktop via the normal Steam UI. The host just attaches to whatever's live
-  and never tears it down, so switching Desktop ↔ Game is rock-solid and disconnecting leaves the box
-  where it was. The streamed game-mode resolution is the box's gamescope mode
-  (`SCREEN_WIDTH/HEIGHT` in `/etc/gamescope-session-plus/sessions.d/steam`), not the client's.
-- **Managed** (`PUNKTFUNK_GAMESCOPE_MANAGED=1`, and remove the attach line) — the host tears the
-  box's gamescope down on connect and launches its **own** at the *client's* exact resolution and
-  refresh, restoring on idle. Client-mode-following, but it can't coexist with a box-owned game-mode
-  session, and there must be **no physical gaming session already running**.
+- **Attach** (`PUNKTFUNK_GAMESCOPE_ATTACH=1`) — the **box** owns its gamescope session and decides
+  Gaming vs Desktop via the normal Steam UI. Game Mode stays on the box's own (physical) display;
+  the host attaches to whatever's live and never tears it down, so switching Desktop ↔ Game is
+  rock-solid and disconnecting leaves the box where it was. When the session is the box's own
+  autologin unit, the host restarts it at the **client's** resolution on a mismatch; a foreign or
+  bare gamescope is streamed at its own mode.
+- **Managed** (the infra-detected default; force with `PUNKTFUNK_GAMESCOPE_MANAGED=1`) — the host
+  takes the box's gamescope session over and relaunches it **headless** at the *client's* exact
+  resolution and refresh — Game Mode runs on the virtual screen, physical displays drop out of it —
+  restoring the box on idle after disconnect.
 
 ## Session following
 
@@ -40,8 +42,8 @@ over its own compositor, and re-targets whichever is live on each switch.
 ## Start the host
 
 On an appliance box (Bazzite, SteamOS) the install guide already enables the host service for you. On
-any other distro running a gamescope session, start it from your session — the default attach model
-just latches onto whatever gamescope session is live:
+any other distro running a gamescope session, just start it — the host auto-detects the live
+gamescope session and picks the model for it:
 
 ```sh
 systemctl --user enable --now punktfunk-host
@@ -56,8 +58,8 @@ a model. See the full [Configuration reference](/docs/configuration) for every o
 
 | Setting | Values | Meaning |
 |---|---|---|
-| `PUNKTFUNK_GAMESCOPE_ATTACH` | `1` | **Attach** model: the box owns its gamescope session; the host captures whatever's live and never tears it down. Streamed resolution is the box's gamescope mode. The default. |
-| `PUNKTFUNK_GAMESCOPE_MANAGED` | `1` | **Managed** model: the host tears the box's gamescope down on connect and launches its own at the client's exact mode, restoring on idle. Doesn't coexist with a box-owned game-mode session. |
+| `PUNKTFUNK_GAMESCOPE_ATTACH` | `1` | **Attach** model: the box owns its gamescope session (on its own display); the host captures whatever's live and never tears it down. A box-owned autologin session is restarted at the client's resolution on a mismatch; a foreign/bare gamescope streams at its own mode. |
+| `PUNKTFUNK_GAMESCOPE_MANAGED` | `1` | **Managed** model (the default where session infra is detected): the host takes the box's gamescope over and relaunches it headless at the client's exact mode, restoring on idle. |
 | `PUNKTFUNK_GAMESCOPE_SESSION` | `steam` | The host owns a `gamescope-session-plus` (Steam) session at the client's mode — a headless appliance with no physical session running. |
 | `PUNKTFUNK_GAMESCOPE_NODE` | `auto` · node id | Discover and capture a **running** gamescope's PipeWire node at a fixed mode. Do **not** combine with `SESSION`. |
 | `PUNKTFUNK_GAMESCOPE_APP` | command | For an ad-hoc bare-gamescope session, the nested command to run (e.g. `vkcube`). |