## Summary
Two docs edits that close a footgun customers persisting transport state
can hit. Clearing `lastEventId` on `chat.endRun()` looks intuitive — the
Run ended, the cursor must be stale — but the cursor is sessionId-keyed,
not runId-keyed. Clearing it forces the next `sendMessages` to subscribe
from `seq_num=0`, which may hit the prior turn's still-durable
`turn-complete` record and close the SSE empty before the new Run's
chunks arrive.
Spells out the invariant in the frontend transport persistence table and
adds a Warning in the `chat.endRun()` reference.
## Test plan
- [x] Mintlify preview renders
- [x] No callout stacking
Eric Allam
c0b9fdfce9