v20260731-000600

Log classifier grouping and coverage improvements (#8404)

- **log-classifier: fix over-broad grouping + close no-match gaps**
- **log-classifier: link fixtures to source jobs + fixture-aware diff
tool**
- **log-classifier: document git difffix for whole-branch fixture
review**
- **log-classifier: surface ninja FAILED: edge over generic
build-stopped**
- **log-classifier: dedupe two noisy catch-all capture groups**