docs: record user-layer decisions, core module map and known gaps

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/TODO.md

@@ -27,4 +27,9 @@ Small, specific, independently actionable. Remove only when actually done.
 - [ ] Admin merge does not merge colliding children recursively; colliding children stay under the tombstoned parent.
 - [ ] Matching: a shared parent resolved without external IDs or position (title/year reuse in
   `packages/core/src/matching.ts`) has no unique key, so concurrent matches can create it twice.
+- [ ] Library search (`q`) and the title sort use the work's title, not the user's `overrides.title`
+  (overrides are a JSON text column). The `tag` filter matches the JSON text with LIKE.
+- [ ] Library hierarchy rollup and orphan detection look three levels deep; deeper trees are not rolled up.
+- [ ] Undoing a per-user move does not move copies or list items back, nor restore aliases that the move
+  re-pointed.
 - [ ] `bun run typecheck` fails with TS18003 until source files exist under `apps/`, `packages/` or `plugins/`.