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/streamdeck/HANDOFF.md

@@ -0,0 +1,82 @@
+# Stream Deck integration — handoff
+
+## Summary
+
+The Elgato Stream Deck plugin (`streamdeck-plugin/`) controls Paarrot via the local HTTP API: toggle mute/deafen, switch channels, send messages, and show status. It is a separate package from the main app but ships in the same monorepo.
+
+## User-facing behavior
+
+- User installs `.streamDeckPlugin` or copies `com.paarrot.streamdeck.sdPlugin` into Stream Deck plugins folder
+- Requires Paarrot desktop running with API on `http://127.0.0.1:33384`
+- Actions: Toggle Mute, Toggle Deafen, Change Channel, Send Message, Get Status
+
+## Architecture
+
+```
+Stream Deck button press
+  → com.paarrot.streamdeck.sdPlugin/plugin/index.js
+    → fetch http://127.0.0.1:33384/...
+      → Paarrot Electron API (see local-api handoff)
+```
+
+## Key files
+
+| Path | Role |
+|------|------|
+| `streamdeck-plugin/com.paarrot.streamdeck.sdPlugin/manifest.json` | Plugin manifest |
+| `streamdeck-plugin/com.paarrot.streamdeck.sdPlugin/plugin/index.js` | Action implementations |
+| `streamdeck-plugin/com.paarrot.streamdeck.sdPlugin/plugin/index.html` | Property inspector UI |
+| `streamdeck-plugin/build.js` | Build `.streamDeckPlugin` bundle |
+| `streamdeck-plugin/validate.js` | Manifest validation |
+| `streamdeck-plugin/README.md` | User install guide |
+| `streamdeck-plugin/QUICKSTART.md` | Dev quickstart |
+
+## Data model
+
+None — stateless HTTP client. Channel list and status come from Paarrot API responses.
+
+## Dependencies
+
+- Elgato Stream Deck software 6.0+
+- Paarrot local API (port 33384)
+- Node build tooling in `streamdeck-plugin/package.json`
+
+## Integration points
+
+- **local-api**: sole backend; breaking API changes require Stream Deck plugin update
+- Icons: `streamdeck-plugin/.../images/paarrot.svg`, `status.svg`
+
+## Testing
+
+### Manual
+
+1. Run Paarrot; confirm `/health` responds.
+2. Load plugin in Stream Deck developer mode.
+3. Map Toggle Mute to a key; join a call; press key.
+4. Map Change Channel; verify room switch in Paarrot.
+
+### Automated
+
+- `node streamdeck-plugin/validate.js`
+
+## Known issues & gotchas
+
+- Plugin repo README still references placeholder GitHub URLs in places — update on publish
+- No auth on API; same machine trust model
+- Deafen/mute only meaningful during active calls
+
+## Future work
+
+- Auto-discover rooms without manual room id entry in property inspector
+- Connection status indicator on Stream Deck key
+
+## Related docs
+
+- [local-api HANDOFF](../local-api/HANDOFF.md)
+- [API.md](../../API.md)
+- [streamdeck-plugin/README.md](../../../../streamdeck-plugin/README.md)
+
+## Add your extra things here
+
+- Bundle id: `com.paarrot.streamdeck`
+- Build output: `.streamDeckPlugin` via `npm run build` in `streamdeck-plugin/`