feat: cw task add CLI command + {AGENT_ID} prompt placeholder

- Add `createTaskForAgent` tRPC mutation: resolves agent → task → phase, creates sibling task
- Add `cw task add <name> --agent-id <id>` CLI command
- Replace `{AGENT_ID}` and `{AGENT_NAME}` placeholders in writeInputFiles() before flushing
- Update docs/agent.md and docs/cli-config.md

apps/server/cli/index.ts

@@ -426,6 +426,32 @@ export function createCli(serverHandler?: (port?: number) => Promise<void>): Com
       }
     });
 
+  // cw task add <name> --agent-id <agentId>
+  taskCommand
+    .command('add <name>')
+    .description('Create a sibling task in the agent\'s current phase')
+    .requiredOption('--agent-id <agentId>', 'Agent ID creating the task')
+    .option('--description <description>', 'Task description')
+    .option('--category <category>', 'Task category (execute, research, verify, ...)')
+    .action(async (name: string, options: { agentId: string; description?: string; category?: string }) => {
+      try {
+        const client = createDefaultTrpcClient();
+        const task = await client.createTaskForAgent.mutate({
+          agentId: options.agentId,
+          name,
+          description: options.description,
+          category: options.category as 'execute' | undefined,
+        });
+        console.log(`Created task: ${task.name}`);
+        console.log(`  ID: ${task.id}`);
+        console.log(`  Phase: ${task.phaseId}`);
+        console.log(`  Status: ${task.status}`);
+      } catch (error) {
+        console.error('Failed to create task:', (error as Error).message);
+        process.exit(1);
+      }
+    });
+
   // Message command group
   const messageCommand = program
     .command('message')