Phase 27: strengthen undo transactions and improve editor workflow

docs/KNOWN_LIMITATIONS.md

@@ -19,7 +19,8 @@
   Automated LADSPA controls use run(1) and can be expensive.
 - GUI loading/compilation is synchronous on the control thread. Timeline grid/
   zoom/selection and graph positions are session UI state. Undo retains 32 edits
-  plus baseline; allocation failures are reported, not silently hidden. Media is
+  plus baseline and at most one reserved metadata snapshot; GUI edits reserve
+  history before mutation/publication. Media is
   never removed by undo/delete. Broad screen-reader/accessibility testing is pending.
 - Format v10 reads v1–v9 and uses relative local media references. External absolute
   media/module paths need manual repair after relocation. Saving does not bundle
@@ -59,3 +60,8 @@ PERFORMANCE.md, PLUGIN_HOSTING.md and RECOVERY.md for tested contracts/evidence.
   for live sine volume/pan/sustain. Live mappings do not drive arranged lanes,
   faders or plugins. No automation capture, touch/latch/write modes or loop
   transport. Backward jumps are deterministic for lanes, not opaque plugin tails.
+
+- Editing feedback remains synchronous; busy cursors are not background loading
+  or cancellable progress. Surviving selections are retained across undo but
+  historical selection/layout is not stored. Native context-menu/focus manual
+  qualification and broad accessibility testing remain pending. See EDITING.md.