fix(scoring): rework penalties, conditional migration mode, cr-id rendering

[dsiddharth2]

Summary

• Penalty matrix rework: Added non-zero penalties for code_style (1.0/0.5/0.25), documentation (1.0/0.5/0.25), and testing (1.5/0.75/0.25) — previously all zero so these categories had no impact on PR score. Bumped architecture penalties to match performance tier (3.0/2.0/1.0).
• Conditional migration mode: Migration mode is no longer always-on for every PR. It now only activates when the PR contains migration-related files (SQL, EF snapshots, Flyway, Alembic). When active, it exempts code_style, documentation, and testing from escalation to critical — an unused import is not a migration risk.
• cr-id rendering fix: Moved <!-- cr-id: xxx --> markers from comment body text to ADO thread properties (CodeHawk.CrId). Azure DevOps inconsistently renders HTML comments as visible text, causing <!-- cr-id: cr-004 --> to show in PR comments. Thread properties are metadata-only and never rendered. Backward compatible — fetch still falls back to comment text parsing for old threads.

Test plan

• All 363 unit tests pass
• Migration mode escalation test updated to verify exempt categories stay at original severity
• New test: test_migration_mode_skips_zero_penalty_categories
• Existing test updated: test_code_style_has_light_penalty (was test_code_style_has_zero_penalty)
• Run a review on a non-migration PR and verify no findings are escalated to critical by migration mode
• Verify cr-id is no longer visible in ADO inline comments
• Verify summary thread detection still works for both old (marker-based) and new (property-based) threads