feat(library/providers): let a provider say how to recognize its games

A plugin's titles launch through the provider's own client, which hands off and
exits — so the host had nothing left to watch, and both lifetime behaviors went
quiet for exactly the entries a provider contributes. A `ProviderEntry` (and a
manual custom entry) may now carry an optional `detect` hint: install dir, exe,
or process name.

It is deliberately a subset of what the host tracks internally. A Steam appid or
a launcher's environment marker are things the host discovers for itself and
would be meaningless — or dangerous — to take on someone's word; where a title
is installed is something only the provider knows. The host's own findings win
where both exist, so a stale export can never redirect the matcher, and a blank
field is treated as absent rather than as "match everything" — an empty install
dir would otherwise prefix-match every process on the box, and this feature can
end processes.

`process_name` is the weakest of the three and the only one typed by hand, so it
is matched case-insensitively against the image's file name and nothing else:
`retroarch` finds RetroArch, not a helper whose name merely starts the same way,
and not a script that happens to live in a `retroarch/` directory. The
never-adopt-a-pre-existing-process rule still bounds it.

Also: the tray summary gains the running-game row (with the closing-in countdown
for a game whose client is gone — visible at the machine without opening the
console), the SDK mirrors the `game.*` events, and its generated client catches
up with the endpoints Phase 1 added.

Gates on .21: check + clippy --all-targets clean, 299 tests, fmt CI-parity,
openapi regenerated (GameEntry still carries no `detect` outbound); SDK tsc +
54 tests green.

plugin-kit/README.md

@@ -45,7 +45,7 @@ export default definePluginKit({
 | `HostClient`, `PluginInfo` | the `pf` facade as services (`request` = the skew-safe untyped seam) |
 | `makeConfigService` | Schema-driven config: raw shape on disk, defaults ONLY in the Schema (`withDecodingDefaultKey` + `encodingStrategy: "omit"`), atomic writes, world-writable refusal, `changes` stream |
 | `makeCacheStore` | disposable derived state (corrupt/absent → empty, write-through) |
-| `ProviderClient` + wire schemas | typed library-provider reconcile over the untyped wire |
+| `ProviderClient` + wire schemas | typed library-provider reconcile over the untyped wire — including the optional `detect` hint (see below) |
 | `makeSyncEngine` | poll + fs-watch + debounce + single-flight coalescing + fingerprint skip + status feed |
 | `serveUi` / `httpApiEnv` | an `effect/unstable/httpapi` HttpApi behind the SDK's `servePluginUi`, core-only layers |
 | `sseRoute` | the status SSE endpoint (httpapi has no event-stream media type) |
@@ -54,6 +54,27 @@ export default definePluginKit({
 | `@punktfunk/plugin-kit/react` | browser glue: `createPluginRouter` (path→hash→fallback deep-link restore + `pf-ui:navigate`), `resolvePluginBase`, `useIsEmbedded`, `ResultGate`, `sseAtom` |
 | `@punktfunk/plugin-kit/theme.css` | the console's violet identity for plugin UIs (import first in your Tailwind entry) |
 
+## Telling the host how to recognize a running title (`detect`)
+
+A `ProviderEntry` may carry an optional `detect` hint:
+
+```ts
+{ external_id: "playnite:9f2…", title: "Hades",
+  launch: { kind: "command", value: "playnite://playnite/start/9f2…" },
+  detect: { install_dir: "D:\\Games\\Hades" } }
+```
+
+It is what lets the host tell that the *game* has exited — which ends the streaming session, so the
+player's client returns to its library instead of showing a bare desktop — and what lets an operator
+who opted into it end the game when the session ends.
+
+Omit it and nothing breaks: the host tracks the process it spawns for your launch command. It matters
+when that command **hands off and exits** — a launcher client, `flatpak run`, a front-end that starts
+an emulator — because then there is nothing left for the host to watch, and both behaviors go quiet
+for that title. Send whatever you genuinely know; `install_dir` is the one to send if you send only
+one, since any process running from under it counts as the game. The host never lets a hint override
+what it worked out itself, and never adopts a process that was already running before the launch.
+
 ## Publishing
 
 Tag `plugin-kit-vX.Y.Z` (matching `package.json`) — `.gitea/workflows/plugin-kit-publish.yml`