fix: serialize patch file mutations

[alexei-ciobanu]

Summary

• wrap each patch hunk's full mutation window in Pi's withFileMutationQueue
• lock move source and destination paths in deterministic order
• canonicalize and deduplicate queue paths to avoid alias deadlocks
• distinguish complete failures from partial failures in tool output
• add coverage for complete-failure wording and concurrent update/move behavior

Validation

• npm test (57 tests)
• npm run check
• concurrent tests repeated 20 times