The gateway's /reset cleanup path called shutdown_memory_provider without
first draining the memory manager's serialized background write worker.
shutdown_all only gives that worker a bounded (~5s) drain and abandons
whatever is still queued past it, so a /reset could silently drop writes
the session had already handed off -- the next session then loaded
stale MEMORY.md.
The CLI exit path already drains via MemoryManager.flush_pending before
shutdown; this PR pins the same contract on the gateway cleanup path.
Cleanup now calls agent._memory_manager.flush_pending(timeout=10) before
the existing shutdown_memory_provider step. The flush is best-effort:
a flush failure must never block teardown, so it is wrapped in
try/except and the existing shutdown path remains the fallback.
Closes#73297
5cc5c58e01