Client now connects to GET /sync/{appId}/stream via fetch + ReadableStream
instead of WebSocket + HTTP pull. Each app gets its own SSE connection that
delivers initial sync data + live updates in one persistent stream.
Changes:
- Remove WebSocket connection (connectUnifiedWs)
- Add connectSSE() per app using fetch + ReadableStream
- Parse SSE events (changes, heartbeat) from streamed response
- Auto-reconnect on disconnect with WS_RECONNECT_DELAY
- Fallback to polling if SSE endpoint not available
- ensureAppSynced() connects SSE for lazy apps on first visit
- handleOnline() reconnects all active SSE streams
- handleOffline() aborts all SSE connections
Benefits: 1 connection instead of 2 (WS + HTTP), data delivered instantly
without notification → pull round-trip, works through HTTP proxies/CDN.
Push (POST /sync/{appId}) remains unchanged.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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