Add group metadata sync for easier group activation

- Sync group names from WhatsApp via groupFetchAllParticipating()
- Store group names in chats table (jid -> name mapping)
- Daily sync with 24h cache, on-demand refresh via IPC
- Write available_groups.json snapshot for agent (main group only)
- Agent can request refresh_groups via IPC if group not found
- Update documentation in main CLAUDE.md and debug skill

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/container-runner.ts

@@ -400,3 +400,34 @@ export function writeTasksSnapshot(
   const tasksFile = path.join(groupIpcDir, 'current_tasks.json');
   fs.writeFileSync(tasksFile, JSON.stringify(filteredTasks, null, 2));
 }
+
+export interface AvailableGroup {
+  jid: string;
+  name: string;
+  lastActivity: string;
+  isRegistered: boolean;
+}
+
+/**
+ * Write available groups snapshot for the container to read.
+ * Only main group can see all available groups (for activation).
+ * Non-main groups only see their own registration status.
+ */
+export function writeGroupsSnapshot(
+  groupFolder: string,
+  isMain: boolean,
+  groups: AvailableGroup[],
+  registeredJids: Set<string>
+): void {
+  const groupIpcDir = path.join(DATA_DIR, 'ipc', groupFolder);
+  fs.mkdirSync(groupIpcDir, { recursive: true });
+
+  // Main sees all groups; others see nothing (they can't activate groups)
+  const visibleGroups = isMain ? groups : [];
+
+  const groupsFile = path.join(groupIpcDir, 'available_groups.json');
+  fs.writeFileSync(groupsFile, JSON.stringify({
+    groups: visibleGroups,
+    lastSync: new Date().toISOString()
+  }, null, 2));
+}