## Summary
Starts **U5** of the package code-organization program after wave 18
(executor peels) landed.
Peels pure free-function clusters out of `self-healing.ts` into
`packages/engine/src/self-healing/` without behavior changes. Public
imports from `./self-healing.js` remain stable via re-exports.
### Peels
| Symbol | New home |
|--------|----------|
| `autoRecoverWorktreeSessionStartFailure` |
`self-healing/auto-recover-worktree-session.ts` |
| `archiveAsGhostBug` | `self-healing/archive-ghost-bug.ts` |
| `hasStepProgress` / work-complete helpers |
`self-healing/step-progress.ts` |
### Line count
- `self-healing.ts`: ~15456 → ~15231 (baseline ratcheted to post-peel
live; main had already drifted past the prior grandfathered ceiling via
organic growth)
- New modules each well under 2,000 lines
## Test plan
- [x] `pnpm --filter @fusion/engine exec tsc --noEmit`
- [x] `self-healing-trait-rekey.test.ts` (autoRecover requeue)
- [x] `self-healing-paused-abort-recovery.test.ts`
- [x] `self-healing-model-unavailable-recovery.test.ts`
- [ ] CI gate
## Follow-ups
U5 Slice B: domain method clusters (startup, in-review, merge-status,
workspace, surfacing) into additional `self-healing/*.ts` modules.
<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit
* **Bug Fixes**
* Improved automatic recovery when worktree sessions fail to start,
including stale or incomplete session data.
* Tasks can be safely requeued while preserving progress, or escalated
after retry limits are reached.
* Improved handling of completed work and failures where task completion
was not recorded.
* Preserved valid task branches during recovery and provided more
reliable fallback requeue behavior.
* Ghost bugs are automatically archived with recovery details and
activity history.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->
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