feat(server,frontend): real-time sync architecture with message accumulator

- Add message-accumulator.js: cascades diff-based message accumulation
- Add 3-second cascade polling with broadcastToAll (was undefined!)
- Add /api/bridge/approve endpoint: tries accept/reject Step→Command→Terminal
- Add persistent approve/reject buttons in chat header toolbar
- Frontend: loadSessionMessages (trajectory + accumulated), applyNewMessages (WS push)
- Status change detection: _prevStatusKey tracking prevents unnecessary re-renders
- actionInProgress flag prevents DOM replacement during button fetch
- Known issues: Trajectory 341 hard limit, Cascade no command-approval state

.agents/workflows/start.md

@@ -48,7 +48,7 @@ git log --oneline -5
 ### 3. Vikunja TODO 태스크
 
 ```powershell
-python .agents\workflows\helpers\vikunja_helper.py list todo
+C:\ProgramData\miniforge3\envs\gravity_web\python.exe .agents\workflows\helpers\vikunja_helper.py list todo
 ```
 
 ### 4. 종합 보고