feat: mount store rw for main agent and add requiresTrigger to register_group

- Mount store/ separately as read-write so the main agent can access
  the SQLite database directly.
- Add requiresTrigger parameter to the register_group MCP tool
  (host IPC already supported it, but the tool never exposed it).
  Defaults to false (no trigger).
- Update group registration instructions to ask user about trigger.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

container/agent-runner/src/ipc-mcp-stdio.ts

@@ -460,6 +460,12 @@ Use available_groups.json to find the JID for a group. The folder name must be c
         'Channel-prefixed folder name (e.g., "whatsapp_family-chat", "telegram_dev-team")',
       ),
     trigger: z.string().describe('Trigger word (e.g., "@Andy")'),
+    requiresTrigger: z
+      .boolean()
+      .optional()
+      .describe(
+        'Whether messages must start with the trigger word. Default: false (respond to all messages). Set to true for busy groups with many participants where you only want the agent to respond when explicitly mentioned.',
+      ),
   },
   async (args) => {
     if (!isMain) {
@@ -480,6 +486,7 @@ Use available_groups.json to find the JID for a group. The folder name must be c
       name: args.name,
       folder: args.folder,
       trigger: args.trigger,
+      requiresTrigger: args.requiresTrigger ?? false,
       timestamp: new Date().toISOString(),
     };