## Summary
Supersedes #3405 — the fork head is not writable from maintainers, so
this branch carries the same fix rebased/merged onto current `main`.
## Conflict resolution
- Main already landed the equivalent fail-open path as **FN-8919**
(`readLinkedTaskOrUndefined` + per-agent try/catch).
- Kept the additional `recoverAgentsRunningOnInactiveTasks` regression
that covers task-gone races plus transient lookup isolation.
- Dropped the duplicate changeset (main already has
`fn-8919-agent-link-sweep-fail-open`).
## Test plan
- [x] `git merge-tree` clean against `main`
- [ ] CI green
Closes context from #3405.
<!-- This is an auto-generated comment: release notes by coderabbit.ai
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## Summary by CodeRabbit
* **Bug Fixes**
* Improved recovery handling when task lookups fail.
* Agents linked to deleted or missing tasks are now unlinked, while
agents affected by temporary errors remain preserved.
* Recovery continues for other eligible agents instead of stopping after
an individual lookup failure.
* **Tests**
* Added regression coverage for deleted, missing, and temporarily
unavailable tasks.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->
Co-authored-by: Codex <codex@openai.com>
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