fix(anime): harden the extension bridge against untrusted repos and hangs

Addresses CodeRabbit review feedback on the Anime Browser:

- reject repository package/apk names that are not plain identifiers, and
  verify the install target resolves inside the extensions directory
- count mpv's %n% option escape in UTF-8 bytes, and escape backslashes in
  header values so a trailing one cannot eat the list separator
- key the bridge extension-id cache by APK content, so an in-place upgrade
  re-uploads instead of running the previous build
- bound every bridge, release-listing, and download request with a timeout
- enforce the APK size limit while streaming rather than after buffering
- read APK bytes on demand instead of holding a base64 copy per extension
  for the lifetime of the browser
- serialize preference mutations and write the file atomically
- handle the sidecar spawn error event, and wait for the child to exit in
  stop() before returning
- report a failed Anime Browser bootstrap instead of showing the starting
  banner forever
- keep the preferences panel's save confirmation and in-flight multi-select
  edits by re-rendering only on a structural schema change

src/animeui/animeui.ts

@@ -488,18 +488,25 @@ api.onBridgeState(renderBridgeState);
 
 void (async () => {
   renderBridgeState({ stage: 'idle', progress: null, message: null });
-  const state = await api.ensureBridge();
-  renderBridgeState(state);
+  try {
+    const state = await api.ensureBridge();
+    renderBridgeState(state);
 
-  const snapshot = await api.getSnapshot();
-  renderSources(snapshot.sources, snapshot.selectedSourceId);
+    const snapshot = await api.getSnapshot();
+    renderSources(snapshot.sources, snapshot.selectedSourceId);
 
-  if (state.stage === 'ready' && snapshot.sources.length > 0) {
-    searchInput.focus();
-    await runSearch('');
-  } else if (state.stage === 'ready') {
-    setStatus(state.message ?? 'No extensions installed.', 'error');
-  } else {
-    setStatus(state.message ?? 'The extension bridge is not available.', 'error');
+    if (state.stage === 'ready' && snapshot.sources.length > 0) {
+      searchInput.focus();
+      await runSearch('');
+    } else if (state.stage === 'ready') {
+      setStatus(state.message ?? 'No extensions installed.', 'error');
+    } else {
+      setStatus(state.message ?? 'The extension bridge is not available.', 'error');
+    }
+  } catch (error) {
+    // Without this the window keeps the "starting" banner up forever, with the
+    // search box disabled and nothing saying why.
+    renderBridgeState({ stage: 'failed', progress: null, message: describe(error) });
+    setStatus(describe(error), 'error');
   }
 })();