## Summary
Follow-up to #2275 review feedback: `getTask` mocks for DUPLICATE
recovery tests now return a default current-task fixture for
non-canonical IDs instead of `undefined`.
## Context
CodeRabbit on #2275 noted that returning `undefined` for every id except
the canonical task could break recovery if the subject task is
re-fetched mid-path.
## Test plan
- [x] `triage-split-into-subtasks-delete.test.ts`
- [x] `triage-finalize-duplicate-lineage.test.ts`
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## Summary by CodeRabbit
* **Tests**
* Improved duplicate-resolution test coverage by preserving task data
during recovery and re-fetch scenarios.
* Added validation for non-canonical task handling to prevent errors
when duplicate tasks are resolved or split.
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