Migration 019 created performance indexes but never recorded itself
in the schema_version table. Without this row the migration runner
considers the schema outdated and would attempt to re-apply. Adds
the standard INSERT INTO schema_version for version 19.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Chain: bd-jec (config flag) -> bd-2yo (fetch MR diffs) -> bd-3qn6 (rewrite who queries)
- Add fetch_mr_file_changes config option and --no-file-changes CLI flag
- Add GitLab MR diffs API fetch pipeline with watermark-based sync
- Create migration 020 for diffs_synced_for_updated_at watermark column
- Rewrite query_expert() and query_overlap() to use 4-signal UNION ALL:
DiffNote reviewers, DiffNote MR authors, file-change authors, file-change reviewers
- Deduplicate across signal types via COUNT(DISTINCT CASE WHEN ... THEN mr_id END)
- Add insert_file_change test helper, 8 new who tests, all 397 tests pass
- Also includes: list performance migration 019, autocorrect module, README updates
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
