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/voice-calls/HANDOFF.md

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+# Voice & video calls — handoff
+
+## Summary
+
+Paarrot supports Matrix RTC voice/video calls via MSC3401 (`org.matrix.msc3401.call.member`) and LiveKit. Calls can be docked in the sidebar, support screen share, remote cursors, mute/deafen, and are wired to the local HTTP API for external control.
+
+## User-facing behavior
+
+- Join/start calls from room UI (when homeserver exposes RTC/LiveKit via `.well-known`)
+- Docked call panel in sidebar; full overlay mode
+- Mute, deafen, camera, screen share controls
+- Call participants shown in room nav (`CallParticipantsIndicator`)
+
+## Architecture
+
+```
+useCallService (CallProvider)
+  → CallService (LiveKit room, Matrix call member state)
+    → useRtcConfig: .well-known m.rtc + LiveKit focus
+  → UI: CallOverlay, DockedCallPanel, SidebarDockedCallPanel
+  → getCallService() global ref for Electron API (paarrot-api.ts)
+```
+
+## Key files
+
+| Path | Role |
+|------|------|
+| `cinny/src/app/features/call/useCall.ts` | React context, global CallService ref |
+| `cinny/src/app/features/call/CallService.ts` | Core call logic |
+| `cinny/src/app/features/call/types.ts` | CallState, ActiveCall, events |
+| `cinny/src/app/features/call/useRtcConfig.ts` | Homeserver RTC / LiveKit discovery |
+| `cinny/src/app/features/call/CallOverlay.tsx` | Full-screen call UI |
+| `cinny/src/app/features/call/DockedCallPanel.tsx` | Docked UI |
+| `cinny/src/app/features/call/SidebarDockedCallPanel.tsx` | Sidebar variant |
+| `cinny/src/app/features/call/useRemoteCursor.ts` | Screen-share cursor sync |
+| `cinny/src/app/features/call/CallSounds.ts` | Join/leave sounds |
+| `cinny/src/app/features/room-nav/CallParticipantsIndicator.tsx` | Nav badge |
+| `cinny/src/types/matrix/room.ts` | `StateEvent.CallMember` |
+
+## Data model
+
+| Key | Scope | Notes |
+|-----|-------|-------|
+| `org.matrix.msc3401.call.member` | Room state | Call membership |
+| LiveKit JWT / room | Ephemeral | From homeserver RTC focus |
+
+Call mute/deafen/video state lives in `CallService` memory, not Matrix account data.
+
+## Dependencies
+
+- `livekit-client` (verify in package.json)
+- Homeserver `.well-known` RTC configuration
+- Browser/Electron media permissions (mic, camera, screen capture)
+- Electron `desktopCapturer` for screen share (main process)
+
+## Integration points
+
+- **local-api**: mute/deafen/status endpoints
+- **Stream Deck**: uses call mute/deafen via API
+- **Room nav**: participant indicators
+- **Electron main**: screen capture IPC if applicable
+
+## Testing
+
+### Manual
+
+1. Use a homeserver with Matrix RTC + LiveKit configured.
+2. Start voice call in a room; verify audio both ways.
+3. Toggle mute/deafen; verify API `/status` reflects state.
+4. Screen share; verify remote cursor if enabled.
+5. Dock/undock call panel.
+
+### Automated
+
+- None identified
+
+## Known issues & gotchas
+
+- `callSupported` false until `.well-known` RTC fetch completes — UI should hide call buttons when unsupported
+- `getCallService()` must be set before API mute actions work
+- Platform differences: screen capture APIs differ Electron vs browser vs Android
+
+## Future work
+
+- Call recording, noise suppression settings
+- Better reconnection / call transfer
+- MSC3401 spec tracking as it stabilizes
+
+## Related docs
+
+- [local-api HANDOFF](../local-api/HANDOFF.md)
+- Matrix MSC3401 (upstream spec)
+
+## Add your extra things here
+
+- `fetchWellKnownWithRTC`, `getLiveKitFocus`, `getLiveKitHomeserverPriority` in `useRtcConfig.ts`
+- Global singleton: `globalCallServiceInstance` in `useCall.ts` for non-React consumers