feat(gateway): wire safe-point runtime cancellation for agent.cancel

src/gateway/session-bridge.ts

@@ -97,6 +97,17 @@ export class SessionBridge {
     if (client) {client.busy = busy;}
   }
 
+  /** Request cancellation for the current operation on a connection's agent. */
+  cancel(connectionId: string): boolean {
+    const client = this.clients.get(connectionId);
+    if (!client || !client.busy) {
+      return false;
+    }
+
+    client.agent.cancel();
+    return true;
+  }
+
   /** Set onToolUse callback for a connection's agent. */
   setOnToolUse(connectionId: string, callback: ((event: ToolUseEvent) => void) | undefined): void {
     const client = this.clients.get(connectionId);