feat(tauri): add low-disk streamed install action

NEXT_STEPS item 1 called out that streamed install was still CLI-only
because the Tauri app started the peer with no stream provider. Users can now
choose an explicit "Low disk install" action from the game detail modal for
remote-only games instead of taking the default archive-preserving download
path.

The GUI command queues a normal peer detail fetch first so the peer database
has the file metadata needed for source validation. A small pending handoff in
Tauri routes the resulting GotGameFiles event into StreamInstallGame instead
of DownloadGameFiles, and clears that pending state on no-peer or download
failure events. This keeps the existing download continuation untouched for
the default action.

The external unrar stream provider moved from the CLI harness into
lanspread-peer so CLI and Tauri use the same implementation. Tauri resolves
the bundled unrar sidecar path and injects that provider at peer startup;
falling back to the noop provider keeps peer startup alive if the sidecar
cannot be resolved, while the streamed install operation still fails safely.

Test Plan:
- just fmt
- just test
- just frontend-test
- just clippy
- just build
- git diff --check

Refs: NEXT_STEPS.md item 1

crates/lanspread-tauri-deno-ts/src/hooks/useGameActions.ts

@@ -9,6 +9,7 @@ export interface GameActions {
     play: (id: string) => Promise<void>;
     startServer: (id: string) => Promise<void>;
     install: (id: string) => Promise<void>;
+    streamInstall: (id: string) => Promise<void>;
     update: (id: string) => Promise<void>;
     uninstall: (id: string) => Promise<void>;
     removeDownload: (id: string) => Promise<void>;
@@ -68,6 +69,15 @@ export const useGameActions = (
         }
     }, [games, settings.language, settings.username]);
 
+    const streamInstall = useCallback(async (id: string) => {
+        try {
+            const success = await invoke<boolean>('stream_install_game', { id });
+            if (success) games.markChecking(id);
+        } catch (err) {
+            console.error('stream_install_game failed:', err);
+        }
+    }, [games]);
+
     const update = useCallback(async (id: string) => {
         try {
             const game = games.games.find(item => item.id === id);
@@ -129,5 +139,15 @@ export const useGameActions = (
         }
     }, []);
 
-    return { play, startServer, install, update, uninstall, removeDownload, cancelDownload, viewFiles };
+    return {
+        play,
+        startServer,
+        install,
+        streamInstall,
+        update,
+        uninstall,
+        removeDownload,
+        cancelDownload,
+        viewFiles,
+    };
 };