Adds a verification system that checks evidence in completed plan items:
- Evidence parsing: supports code locations (file:line, file:line-line, file only)
and test references (file::test_name)
- Code location verification: checks file exists, validates line numbers in range
- Test reference verification: checks test file exists, searches for fn pattern
- Verification results: Verified, Warning, Error, Skipped statuses
- Loud output formatting with emoji indicators for warnings/errors
- Integration with execute_plan_write(): runs when plan is complete and approved
- 12 new unit tests covering parsing and verification
Warnings are advisory (don't block), errors are loud but also don't block.
Blocked items are skipped during verification.
d6b7177107