feat(collab): local-ops-only undo — remote applies skip the undo stack (ysync miss 09)

Ctrl+Z after a peer's edit no longer reverts (and re-broadcasts) the
peer's work, and the adopt undo-bomb is gone:

- doApply/doApplyItems (both editors) Push with SKIP_UNDO; the emit path
  is unaffected (suppression keys off s_applyingRemote, not undo).
- With SKIP_UNDO no picker owns removed items — the bindings free them
  after Push (explicit removals + upsert's remove-before-re-add; fields
  excluded: CHT_REMOVE hides them, parent keeps ownership). Freeing stays
  out of the fork commit classes so DRC's SKIP_UNDO callers can't
  double-free.
- Test hooks kicadCollabTestUndo/UndoDepth, registered per-editor AND in
  the kicad_editor dispatcher (merged image compiles out per-app
  registrations).
- kicad pointer: eeschema UUID undo guard + SKIP_UNDO connectivity split
  + quiet stale-entry drop (ca8877324c).
- tests/kicad/collab-undo.spec.ts: 5 scenarios (no undo entry from remote
  applies; selective undo; stranded replaced/deleted entries) — 5/5, plus
  collab/ysync regression 30 pass.
- docs: ysync-review 20 fix record; 09 marked FIXED; overview indexed.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_019ejJEvS7ogef2o9gVTXjmp

docs/features/ysync-review/09-miss-undo-not-collab-aware.md

@@ -1,7 +1,8 @@
 # Design miss 09 — Undo is not collab-aware: Ctrl+Z reverts peers' work and re-broadcasts it
 
 **Severity:** design gap (converges, but with surprising and destructive UX)
-**Status:** open decision
+**Status:** FIXED 2026-07-07 — option 1 implemented, see
+[20-fix-miss09-collab-aware-undo.md](20-fix-miss09-collab-aware-undo.md)
 
 ## Where