fix(events): reclaim provably-dead orphaned endpoint claims instead of failing permanently

[ScriptedAlchemy]

Summary

• A process killed between claiming <endpoint>.lock and releasing it previously bricked the endpoint: every later startup hit EEXIST, exhausted the bounded retries, and failed until someone manually removed the undocumented lock file.
• The claim now records owner identity (pid, plus /proc/<pid>/stat starttime on Linux) in the lockfile immediately after the exclusive open. On EEXIST with a non-live socket, a contender reclaims only when the owner is provably dead — ESRCH, or a live pid whose starttime mismatches (recycled pid, Linux) — deleting the orphan guarded by the same dev+inode identity check the release path already uses, then re-racing the wx open so exactly one contender wins.
• Live claims are never stolen; empty/garbage/unverifiable lockfiles and non-Linux liveness ambiguity keep the existing fail-closed bounded-retry behavior. Identity and stat are read from a single file handle, so the reclamation guard can't act on a different file than the one whose contents were verified. No TOCTOU regression against the fix(events): claim the IPC endpoint atomically before removing stale sockets (#209 follow-up) #216 design.

Addresses the unresolved P2 Codex finding on #216 (packages/agent-bundle/src/events/ipc.ts claim retries).

Test plan

• pnpm test:unit packages/agent-bundle/tests/event-ipc.test.ts — new coverage: killed-owner reclamation, live-owner fail-closed, garbage-lockfile fail-closed, recycled-pid reclamation (asserts the live child is untouched); 5 failures when the source fix is reverted
• pnpm typecheck / pnpm lint clean

[changeset-bot]

🦋 Changeset detected

Latest commit: d02cffc

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
agent-bundle	Patch

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[chatgpt-codex-connector]

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Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-09-01T23:04:49.391366Z	d02cffc	PR opened

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Reviewed commit: d02cffc339

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