fix: pass subagent_enabled in gateway-client.ts synchronous path

The connectZclawStream call in the synchronous code path (common case
when agentId is already known) was missing the subagent_enabled field,
causing Gateway-connected clients to never send the flag to the server.

desktop/src/lib/gateway-client.ts

@@ -516,6 +516,7 @@ export class GatewayClient {
       thinking_enabled: opts?.thinking_enabled,
       reasoning_effort: opts?.reasoning_effort,
       plan_mode: opts?.plan_mode,
+      subagent_enabled: opts?.subagent_enabled,
     });
 
     return { runId };