merge: task 5 works and matching

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

docs/TODO.md

@@ -24,4 +24,7 @@ Small, specific, independently actionable. Remove only when actually done.
     file, and compare steps and token use.
 
 ## Known issues
+- [ ] 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.
 - [ ] `bun run typecheck` fails with TS18003 until source files exist under `apps/`, `packages/` or `plugins/`.