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

wasm/bindings/kicad_editor_embind.cpp

@@ -45,6 +45,9 @@ std::string pcbCollabTestMoveFirst( int aDx, int aDy );
 std::string pcbCollabGetPos( std::string aId );
 bool        pcbCollabTestRemoveItem( std::string aId );
 bool        pcbCollabTestRotateItem( std::string aId, double aDeg );
+// Collab-aware undo (ysync miss 09).
+bool        pcbCollabTestUndo();
+int         pcbCollabTestUndoDepth();
 // Presence (collab-presence 0002) + comment pins/panning (0005).
 void        pcbCollabPresenceStart();
 void        pcbCollabSetRemote( std::string aJson );
@@ -74,6 +77,9 @@ std::string schCollabTestMoveFirst( int aDx, int aDy );
 std::string schCollabGetPos( std::string aId );
 bool        schCollabTestRemoveItem( std::string aId );
 bool        schCollabTestRotateItem( std::string aId, double aDeg );
+// Collab-aware undo (ysync miss 09).
+bool        schCollabTestUndo();
+int         schCollabTestUndoDepth();
 // Presence (collab-presence 0003 — eeschema counterparts) + pins (0005).
 void        schCollabPresenceStart();
 void        schCollabSetRemote( std::string aJson );
@@ -171,6 +177,16 @@ static bool collabTestRotateItem( std::string aId, double aDeg )
                              : schCollabTestRotateItem( aId, aDeg );
 }
 
+static bool collabTestUndo()
+{
+    return pcbEditorActive() ? pcbCollabTestUndo() : schCollabTestUndo();
+}
+
+static int collabTestUndoDepth()
+{
+    return pcbEditorActive() ? pcbCollabTestUndoDepth() : schCollabTestUndoDepth();
+}
+
 // Presence shims (collab-presence 0002 pcbnew / 0003 eeschema): route to the live
 // editor's implementation, same pattern as the collab bridge shims above.
 static void collabPresenceStart()
@@ -271,6 +287,9 @@ EMSCRIPTEN_BINDINGS(kicad_editor) {
     // endpoint, field text — flow from the per-editor blocks unchanged).
     function("kicadCollabTestRemoveItem", &collabTestRemoveItem);
     function("kicadCollabTestRotateItem", &collabTestRotateItem);
+    // Collab-aware undo (ysync miss 09).
+    function("kicadCollabTestUndo", &collabTestUndo);
+    function("kicadCollabTestUndoDepth", &collabTestUndoDepth);
     // Presence (collab-presence 0002/0003) + comment pins/panning (0005).
     function("kicadCollabPresenceStart", &collabPresenceStart);
     function("kicadCollabSetRemote", &collabSetRemote);