* fix(events): preserve thread seq watermark across run deletion
* fix(events): clean up watermarks for empty threads
* perf(events): avoid duplicate fence on run deletion
delete_by_run already reaches _max_seq_for_thread, which acquires the transaction-scoped thread mutation fence. Keep the count and delete under that same transaction lock without taking the Postgres advisory lock twice, and pin the single acquisition in the existing test.
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Co-authored-by: yu1128-L <296164533+yu1128-L@users.noreply.github.com>
Co-authored-by: Willem Jiang <willem.jiang@gmail.com>
* fix(events): serialize DB deletion with thread writers
* fix(runs): delete thread history without dropping reservations
* fix(feedback): support owner-scoped thread cleanup
* fix(threads): clean persisted records on deletion
* fix(threads): correct the feedback cleanup rationale
* test(runs): drop the wall-clock probe from the in-flight delete test
* docs: record the thread-delete and event-store fence contracts
* fix(threads): preserve legacy event-store delete compatibility
