Completes what the env-lock fix started. `apply_input_env` published its decision into
PUNKTFUNK_GAMESCOPE_NODE/_SESSION and `GamescopeDisplay::create` read it back out —
with the lock released in between, and with the GameStream plane, the mid-stream
switch watcher and the capture-loss rebuild all re-running the writer. So session B's
routing decision could retarget session A's `create`: A asks for a bare spawn, B
connects, A attaches to B's session instead.
The decision now travels as a `GamescopeRoute` return value and is carried on the
backend INSTANCE via `set_gamescope_route` — the discipline `set_launch_command`
already documents two lines above it ("Carried on the backend instance — NOT a
process-global env var — so concurrent sessions can't stomp each other's launch
target"). Nothing writes the two keys any more; they are read once, as operator
overrides, and `create`/`poolable_now`/`launch_is_nested` all answer from the
session's own route.
The route carries its payload rather than just the verdict, so the managed session
flavour and the attach node id stop being separate env reads too.
Threaded through both planes: handshake -> SessionContext -> `vd`, and the GameStream
`open_source` -> `run`. Three re-resolution points needed the same treatment and each
would have silently downgraded a session to a bare spawn without it — the switch
watcher's rebuilt backend, the capture-loss rebuild (which can swap the whole
instance), and the operator-pinned path, which deliberately skips the input-backend
write but still needs a route. That last one is why the ladder is split out as
`resolve_gamescope_route`: a `PUNKTFUNK_COMPOSITOR` pin must not silently mean "bare
spawn" on a box pinned to the managed session.
`#[must_use]` on both entry points found the capture-loss site, which I had missed.
Verified on 192.168.1.21: whole workspace `cargo check -p punktfunk-host`, clippy
--all-targets clean over the host and pf-vdisplay, 100 pf-vdisplay tests, and the live
GNOME create/drop still green. Windows + Linux xcheck clean on the Mac.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
enricobuehlerandClaude Opus 5
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