fix(api): reconcile runs and threads after worker loss (#484)

* fix(api): reconcile runs and threads after worker loss

* fix(api): harden run reconciliation

* fix(api): close run cancellation races

* fix(api): harden run reconciliation races

* refactor(api): remove obsolete run status hooks

* docs(api): clarify stale-worker interruption

* fix(api): harden cancellation cleanup

* fix(api): preserve cancellation after cleanup failure

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Co-authored-by: open-swe[bot] <open-swe@users.noreply.github.com>