- Add AiSessionStore.ping() and expose POST /api/ai-sessions/:id/ping for lightweight heartbeat updates without emitting high-frequency session events
- Add pingSession() client API and integrate 25s keep-alive timers into planning, subtask, and mission interview resilient SSE connections
- Ensure keep-alive timers stop on stream completion, fatal errors, and explicit close while treating ping failures as best-effort non-fatal behavior
- Expand API/store/routes coverage with targeted tests for ping endpoint behavior, ping store semantics, and SSE keep-alive lifecycle handling
- Stabilize MissionStore latest-error lookup ordering with a rowid tiebreaker when timestamps are equal
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