refactor: separate Layers panel presentation from lifecycle actions

src/ui/clearLayersControl.js

@@ -0,0 +1,18 @@
+/** Keep the clear action focusable while busy; the caller owns its transaction. */
+export function bindClearLayersControl(button, clear) {
+  let destroyed = false;
+  const click = () => { if (!destroyed) void clear(); };
+  button?.addEventListener('click', click);
+  return {
+    setBusy(busy) {
+      if (destroyed || !button) return;
+      button.setAttribute('aria-disabled', String(busy));
+      button.setAttribute('aria-busy', String(busy));
+      button.setAttribute('aria-label', busy ? 'Clearing selected data layers' : 'Clear selected data layers');
+    },
+    destroy() {
+      destroyed = true;
+      button?.removeEventListener('click', click);
+    },
+  };
+}