Add register_group IPC command for dynamic group registration

Main agent can now register new groups via MCP tool without restart.
Host updates both in-memory state and JSON file, creates group folders.
Authorization enforced at both agent and host level.

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

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

@@ -276,6 +276,45 @@ SCHEDULE VALUE FORMAT (all times are LOCAL timezone):
             }]
           };
         }
+      ),
+
+      tool(
+        'register_group',
+        `Register a new WhatsApp group so the agent can respond to messages there. Main group only.
+
+Use available_groups.json to find the JID for a group. The folder name should be lowercase with hyphens (e.g., "family-chat").`,
+        {
+          jid: z.string().describe('The WhatsApp JID (e.g., "120363336345536173@g.us")'),
+          name: z.string().describe('Display name for the group'),
+          folder: z.string().describe('Folder name for group files (lowercase, hyphens, e.g., "family-chat")'),
+          trigger: z.string().describe('Trigger word (e.g., "@Andy")')
+        },
+        async (args) => {
+          if (!isMain) {
+            return {
+              content: [{ type: 'text', text: 'Only the main group can register new groups.' }],
+              isError: true
+            };
+          }
+
+          const data = {
+            type: 'register_group',
+            jid: args.jid,
+            name: args.name,
+            folder: args.folder,
+            trigger: args.trigger,
+            timestamp: new Date().toISOString()
+          };
+
+          writeIpcFile(TASKS_DIR, data);
+
+          return {
+            content: [{
+              type: 'text',
+              text: `Group "${args.name}" registered. It will start receiving messages immediately.`
+            }]
+          };
+        }
       )
     ]
   });