feat: implement 18 NOTE beads — per-note search and document pipeline

Tier 0 (Ingestion):
- NOTE-0A: Upsert/sweep for issue discussion notes (stable IDs)
- NOTE-0B: Immediate deletion propagation for swept notes
- NOTE-0C: Sweep safety guard for partial fetch protection
- NOTE-0D: Capture immutable author_id in note upserts

Tier 1 (Query/CLI):
- NOTE-1A: Note query layer data types and filters (28+ filter combinations)
- NOTE-1B: CLI arguments and command wiring for lore notes
- NOTE-1C: Human and robot output formatting (table/json/jsonl/csv)
- NOTE-1D: robot-docs integration for notes command
- NOTE-1E: Migration 022 — composite query indexes + author_id column

Tier 2 (Document/Search):
- NOTE-2A: Migration 024 — schema rebuild for note documents
- NOTE-2B: SourceType::Note enum extension
- NOTE-2C: Note document extractor function
- NOTE-2D: Regenerator and dirty tracking for note documents
- NOTE-2E: Generate-docs full rebuild support for notes
- NOTE-2F: Search CLI --type note support
- NOTE-2G: Parent metadata change propagation to note documents
- NOTE-2H: Migration 025 — backfill existing notes after upgrade
- NOTE-2I: Batch parent metadata cache for note regeneration

21 files changed, 5364 insertions, 713 tests passing.

migrations/022_notes_query_index.sql

@@ -0,0 +1,21 @@
+-- Migration 022: Composite query indexes for notes + author_id column
+-- Optimizes author-scoped and project-scoped date-range queries on notes.
+-- Adds discussion JOIN indexes and immutable author identity column.
+
+-- Composite index for author-scoped queries (who command, notes --author)
+CREATE INDEX IF NOT EXISTS idx_notes_user_created
+ON notes(project_id, author_username COLLATE NOCASE, created_at DESC, id DESC)
+WHERE is_system = 0;
+
+-- Composite index for project-scoped date-range queries
+CREATE INDEX IF NOT EXISTS idx_notes_project_created
+ON notes(project_id, created_at DESC, id DESC)
+WHERE is_system = 0;
+
+-- Discussion JOIN indexes
+CREATE INDEX IF NOT EXISTS idx_discussions_issue_id ON discussions(issue_id);
+CREATE INDEX IF NOT EXISTS idx_discussions_mr_id ON discussions(merge_request_id);
+
+-- Immutable author identity column (GitLab numeric user ID)
+ALTER TABLE notes ADD COLUMN author_id INTEGER;
+CREATE INDEX IF NOT EXISTS idx_notes_author_id ON notes(author_id) WHERE author_id IS NOT NULL;