## Summary
- keep persisted operator-routed external checkouts authoritative during
executor recovery, remediation, verification, and cleanup
- fail closed when a configured external route is invalid instead of
falling back to a Fusion-managed worktree
- prevent Fusion from cleaning up operator-owned external checkouts
- add dashboard and executor regression coverage for the routing
handoffs
## Test plan
- `pnpm --filter @fusion/engine exec vitest run
src/__tests__/verify-worktree-invariants-missing.test.ts`
- `pnpm --filter @fusion/engine exec vitest run
src/__tests__/external-execution-checkout.test.ts
src/__tests__/executor-triage-column-audit.test.ts`
- `pnpm --filter @fusion/engine exec vitest run
src/__tests__/executor-fast-mode-workflows.test.ts -t 'external
execution|authoritative executor route|completed-task recovery captures
the live external|pre-merge remediation reuses the live external'`
- `FUSION_DASHBOARD_DEEP=1 pnpm --filter @fusion/dashboard exec vitest
run src/__tests__/routes-tasks-near-duplicate.test.ts -t 'PATCH
external-checkout persists one clean Git checkout for execution and
review'`
- `pnpm --filter @fusion/engine typecheck`
- `pnpm --filter @fusion/dashboard typecheck`
- `pnpm test:gate:static`
- `pnpm check:changesets --strict`
<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit
- **Bug Fixes**
- Improved external checkout routing across execution, verification,
recovery, retries, and remediation.
- Operations now use the latest persisted checkout details, preventing
stale routing information from directing work to the wrong location.
- Invalid or missing checkout routes fail safely with clear verification
errors.
- External checkouts are protected from unintended managed worktree or
branch cleanup.
- **Documentation**
- Clarified external checkout routing and validation behavior.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->
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