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/direct-messages/HANDOFF.md

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+# Direct messages — handoff
+
+## Summary
+
+The DMs panel lists direct chats and provides flows to start new conversations. Uses `m.direct` account data to identify DM rooms.
+
+## User-facing behavior
+
+- Sidebar Direct tab shows DM rooms sorted
+- Create new DM / group chat
+- DM room opens in direct route layout
+- Paarrot logo badge states on tab (shared with home tab styling)
+
+## Architecture
+
+```
+client/direct/
+  Direct.tsx — DM room list page
+  DirectCreate.tsx — start new chat
+  useDirectRooms.ts — room list from m.direct
+  RoomProvider.tsx — route-level room context
+mDirectAtom — direct room index
+```
+
+## Key files
+
+| Path | Role |
+|------|------|
+| `cinny/src/app/pages/client/direct/Direct.tsx` | DM list |
+| `cinny/src/app/pages/client/direct/DirectCreate.tsx` | Create DM |
+| `cinny/src/app/pages/client/direct/useDirectRooms.ts` | List logic |
+| `cinny/src/app/pages/client/sidebar/DirectTab.tsx` | Sidebar tab |
+| `cinny/src/app/state/mDirectList.ts` | `mDirectAtom` |
+| `cinny/src/app/hooks/useDirectUsers.ts` | DM user helpers |
+
+## Data model
+
+| Key | Scope |
+|-----|-------|
+| `m.direct` | User account data — map userId → roomIds[] |
+
+## Dependencies
+
+- matrix-js-sdk DM APIs
+- `is_direct` on member events
+
+## Integration points
+
+- **home-and-sidebar**: DirectTab
+- **routing-and-navigation**: `DIRECT_PATH`
+- **create-flows**: create-chat feature
+- **room-timeline**: same Room component for DM rooms
+
+## Testing
+
+### Manual
+
+1. Start DM with user; appears in direct list.
+2. Group DM with multiple users.
+3. Unread badge on Direct tab.
+
+### Automated
+
+- None
+
+## Known issues & gotchas
+
+- `m.direct` can be stale — client may repair on sync
+- DM vs private room distinction relies on account data
+
+## Future work
+
+- Pin favorite DMs
+- DM search filter
+
+## Related docs
+
+- [home-and-sidebar HANDOFF](../home-and-sidebar/HANDOFF.md)
+- [create-flows HANDOFF](../create-flows/HANDOFF.md)
+
+## Add your extra things here
+
+- `getDirectRoomPath` in pathUtils for DM room URLs