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

src/gateway/handlers/agent.ts

@@ -182,8 +182,6 @@ export function createAgentHandlers(deps: AgentHandlerDeps) {
     },
 
     'agent.cancel': async (request: GatewayRequest): Promise<OutboundMessage> => {
-      // Cancel is a placeholder — proper cancellation requires abort controller support in NativeAgent.
-      // For now, just report whether the agent was busy.
       const params = request.params as { connectionId?: string } | undefined;
       const connectionId = params?.connectionId as string;
 
@@ -191,9 +189,22 @@ export function createAgentHandlers(deps: AgentHandlerDeps) {
         return makeError(request.id, ErrorCode.InvalidRequest, 'connectionId is required');
       }
 
-      const wasBusy = deps.sessionBridge.isBusy(connectionId);
-      // TODO: Wire AbortController into NativeAgent for actual cancellation
-      return { id: request.id, result: { cancelled: wasBusy } };
+      const sessionId = deps.sessionBridge.getSessionId(connectionId);
+      const laneId = sessionId ?? connectionId;
+
+      // Clear any queued (not-yet-started) work first.
+      deps.laneQueue.cancel(laneId);
+
+      const cancelled = deps.sessionBridge.cancel(connectionId);
+      return {
+        id: request.id,
+        result: {
+          cancelled,
+          message: cancelled
+            ? 'Cancellation requested. The active operation will stop at the next safe point.'
+            : 'No active operation to cancel.',
+        },
+      };
     },
   };
 }