review fix: pin ordinary-send batching removal

docs/core-data-structures/persistence.md

@@ -6,7 +6,7 @@ The seam is a textbook [capability seam](../../.agents/notes/implemented/archite
 
 ## The flush checkpoint
 
-`session/event` is a *synchronous* notification; persistence plugins buffer it (write-behind) and drain at the awaited `session/flush` checkpoint the loop fires at every turn end. The next turn waits for that checkpoint to settle. A successful flush durably commits the closed turn as one unit; a rejecting flush is reported via `agent/error` and the logger — never as a session event (it would land past the closed turn) — and does not prevent the next turn, while the backend keeps its buffered events for the next flush.
+`session/event` is a *synchronous* notification; persistence plugins buffer it (write-behind) until `session/flush`. The loop awaits an ordinary turn's checkpoint before claiming the next queue item; synchronous idle `inject()` schedules its checkpoint without blocking `send()`, and disposal still drains it. A successful flush durably commits the closed turn as one unit; a rejecting flush is reported through `agent/error` and the logger — never as a session event past the closed turn — while the backend keeps its buffered events for the next flush.
 
 ## Crash recovery preserves an interrupted turn