feat: upgrade toolchain and soften sync recovery after network blips

Bump Vite 8, matrix-js-sdk, and related deps; fix immer/vanilla-extract imports for new majors. Replace blocking sync error dialog with background recovery on wake/offline, and disable Vite auto-open in dev. Add feature handoff documentation index.

docs/handoff/features/local-api/HANDOFF.md

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+# Local HTTP API — handoff
+
+## Summary
+
+Paarrot exposes a localhost HTTP API (port **33384**) so external tools — Stream Deck, scripts, macros — can control the running desktop app: mute/deafen, switch rooms, send messages, and read status. The Electron main process runs an Express server; actions are forwarded to the renderer via IPC and executed against the live Matrix client and call service.
+
+## User-facing behavior
+
+- API starts automatically when the Electron app launches (no user setting).
+- Only binds to `127.0.0.1` — not reachable from the network.
+- No authentication today; security relies on localhost-only binding.
+
+## Architecture
+
+```
+External client (curl, Stream Deck, script)
+  → GET/POST http://127.0.0.1:33384/...
+    → electron/api-server.js (Express)
+      → IPC to renderer (executeAction)
+        → cinny/src/app/paarrot-api.ts (initPaarrotAPI)
+          → Matrix client / CallService / router navigate
+```
+
+Navigation for room changes uses `setPaarrotNavigate()` registered from the React router in `ClientNonUIFeatures.tsx`.
+
+## Key files
+
+| Path | Role |
+|------|------|
+| `electron/api-server.js` | Express routes, IPC bridge to renderer |
+| `electron/main.js` | Starts `PaarrotAPIServer` with the main window |
+| `cinny/src/app/paarrot-api.ts` | Action handlers (mute, deafen, channel, message, status) |
+| `cinny/src/app/pages/client/ClientNonUIFeatures.tsx` | Calls `initPaarrotAPI()` and `setPaarrotNavigate()` |
+| `test-api.js` / `test-api.sh` | Smoke tests for endpoints |
+| `paarrot-api.postman_collection.json` | Postman collection (generated) |
+
+## Data model
+
+No persistent storage. Actions read/write ephemeral app state (current room, call mute/deafen).
+
+### IPC actions (renderer)
+
+| Action | Params | Returns |
+|--------|--------|---------|
+| `get-status` | — | mute, deafen, currentRoom, connected, userId |
+| `toggle-mute` / `set-mute` | `{ muted? }` | `{ muted }` |
+| `toggle-deafen` / `set-deafen` | `{ deafened? }` | `{ deafened }` |
+| `change-channel` | `{ roomId }` | navigation result |
+| `get-channels` | — | room list |
+| `send-message` | `{ roomId, message }` | send result |
+| `send-message-current` | `{ message }` | send to active room |
+| `get-current-room` | — | current room id |
+
+## Dependencies
+
+- `express`, `cors`, `body-parser` (Electron)
+- `matrix-js-sdk` (renderer)
+- Call feature: `getCallService()` from `features/call/useCall.ts`
+
+## Integration points
+
+- **Voice calls**: mute/deafen actions delegate to `CallService`
+- **Stream Deck**: `streamdeck-plugin/` consumes this API
+- **Room navigation**: uses `getHomeRoomPath`, `getDirectRoomPath`, `getSpaceRoomPath`
+- **Space detection**: `isSpaceLikeRoom()` checks `im.paarrot.room.kind` and `m.forum` type
+
+## Testing
+
+### Manual
+
+1. Start Paarrot desktop (`npm run dev` or built app).
+2. `curl http://127.0.0.1:33384/health` → `{ "status": "ok" }`
+3. `curl http://127.0.0.1:33384/status` while logged in.
+4. Join a voice call; `POST /mute/toggle` and verify UI state.
+5. `POST /channel` with a room id; verify navigation.
+
+### Automated
+
+- `node test-api.js` from repo root
+
+## Known issues & gotchas
+
+- Mute/deafen only work when `CallService` has an active call; otherwise handlers return a message, not an error.
+- API is Electron-only; `initPaarrotAPI` no-ops when `window.electron.api` is missing (web/Tauri builds).
+- Adding endpoints requires changes in **both** `api-server.js` and `paarrot-api.ts`.
+
+## Future work
+
+- Optional auth token for local API
+- WebSocket or SSE for status push (Stream Deck polling today)
+- Document all endpoints in Postman collection generator (`scripts/generate-postman-collection.js`)
+
+## Related docs
+
+- [API.md](../../API.md) — full endpoint reference
+- [API-QUICKSTART.md](../../API-QUICKSTART.md)
+- [streamdeck HANDOFF](../streamdeck/HANDOFF.md)
+
+## Add your extra things here
+
+- Default port: **33384** (`PaarrotAPIServer` constructor in `api-server.js`)
+- `isSpaceLikeRoom` treats `forum_space` room kind and `m.forum` create type as spaces for channel listing