feat: implement per-note search and document pipeline

- Add SourceType::Note with extract_note_document() and ParentMetadataCache
- Migration 022: composite indexes for notes queries + author_id column
- Migration 024: table rebuild adding 'note' to CHECK constraints, defense triggers
- Migration 025: backfill existing non-system notes into dirty queue
- Add lore notes CLI command with 17 filter options (author, path, resolution, etc.)
- Support table/json/jsonl/csv output formats with field selection
- Wire note dirty tracking through discussion and MR discussion ingestion
- Fix test_migration_024_preserves_existing_data off-by-one (tested wrong migration)
- Fix upsert_document_inner returning false for label/path-only changes

src/cli/commands/search.rs

@@ -334,6 +334,7 @@ pub fn print_search_results(response: &SearchResponse) {
             "issue" => "Issue",
             "merge_request" => "MR",
             "discussion" => "Discussion",
+            "note" => "Note",
             _ => &result.source_type,
         };