F3 SLICE-3: applyAgentEdit seam + live tracking + decorations/toggle (INV-7/INV-9) (#6)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/pendingEdits.ts

@@ -24,7 +24,11 @@ export class PendingEditRegistry {
     this.pending.push(edit);
   }
 
-  /** Remove a registration that failed to apply. */
+  /**
+   * Remove a registration that failed to apply. Identity-based (`===`), so
+   * callers must keep the exact registered object; it is a no-op when `match`
+   * already consumed the registration.
+   */
   unregister(edit: PendingEdit): void {
     this.pending = this.pending.filter((p) => p !== edit);
   }