feat(app): expose local sharing and verified transfers

Add a durable, acknowledged Local network sharing switch with fail-closed
hydration, serialized mutation, and redacted ephemeral-identity diagnostics.
Keep local Call-to-Play state available while gating every network action on the
effective sharing generation.

Render revisioned verification, invalid-source retry, and sticky source
exhaustion states. Preserve opaque attempt IDs through progress delivery so
out-of-order webview events cannot attach stale bytes to a successor transfer,
and keep terminal exhaustion visible after the last source departs.

Own listeners, native invokes, persistence, dialogs, and companion-window
creation through webview close. Late creation is settled and cleaned before the
parent realm is destroyed.

Test Plan:
- `just frontend-test` -- passed (91/91)
- `just build` -- passed with TypeScript, Vite, and release Tauri compilation
- `just test` -- passed on the completed stack (708 workspace tests)
- `just clippy` -- passed on the completed stack
- `git diff --cached --check` -- passed

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

@@ -1,28 +1,41 @@
-import { useCallback, useRef, useState } from 'react';
+import { useCallback, useEffect, useRef, useState } from 'react';
 import { invoke } from '@tauri-apps/api/core';
 
+import {
+    createThumbnailRequestKey,
+    startOwnedThumbnailGeneration,
+    ThumbnailRequestGeneration,
+    thumbnailIdsFromRequestKey,
+} from '../lib/thumbnailRequests';
+import { windowAsyncScope } from '../lib/asyncOwnership';
+
 /**
- * Lazy, per-id cache for cover thumbnails. Returns `null` until the value is
- * known; returns the empty string when the backend has nothing for the id, so
- * callers can fall back to the placeholder cover art.
+ * Per-id cache for cover thumbnails belonging to the supplied game ids.
+ * Returns `null` until the value is known; returns the empty string when the
+ * backend has nothing for the id, so callers can use the placeholder cover.
  */
-export const useThumbnails = () => {
+export const useThumbnails = (ids: readonly string[]) => {
     const [thumbnails, setThumbnails] = useState<Map<string, string>>(new Map());
-    const pending = useRef<Set<string>>(new Set());
+    const thumbnailsRef = useRef(thumbnails);
+    const requestKey = createThumbnailRequestKey(ids);
+
+    useEffect(() => {
+        const generation = new ThumbnailRequestGeneration(
+            id => invoke<string>('get_game_thumbnail', { gameId: id }),
+            (id, url) => {
+                const next = new Map(thumbnailsRef.current).set(id, url);
+                thumbnailsRef.current = next;
+                setThumbnails(next);
+            },
+        );
+        const missingIds = thumbnailIdsFromRequestKey(requestKey)
+            .filter(id => !thumbnailsRef.current.has(id));
+
+        return startOwnedThumbnailGeneration(windowAsyncScope, generation, missingIds);
+    }, [requestKey]);
 
     const get = useCallback((id: string): string | null => {
         if (thumbnails.has(id)) return thumbnails.get(id) ?? '';
-        if (pending.current.has(id)) return null;
-        pending.current.add(id);
-        invoke<string>('get_game_thumbnail', { gameId: id })
-            .then(url => {
-                pending.current.delete(id);
-                setThumbnails(prev => new Map(prev).set(id, url));
-            })
-            .catch(() => {
-                pending.current.delete(id);
-                setThumbnails(prev => new Map(prev).set(id, ''));
-            });
         return null;
     }, [thumbnails]);