ext(sw): add list_groups popup handler

extension/src/service-worker/router/popup-only.ts

@@ -159,6 +159,16 @@ export async function handle(
       return { ok: true, data: { url: tab.url, title: tab.title ?? '' } };
     }
 
+    case 'list_groups': {
+      if (!state.manifest) return { ok: true, data: { groups: [] } };
+      const set = new Set<string>();
+      for (const id in state.manifest.items) {
+        const g = state.manifest.items[id].group;
+        if (g) set.add(g);
+      }
+      return { ok: true, data: { groups: Array.from(set).sort() } };
+    }
+
     case 'generate_password': {
       const password = state.wasm.generate_password(JSON.stringify(msg.request));
       return { ok: true, data: { password } };