feat(n8n-runner): support async response handling (#2487)

* feat(n8n-runner): support async response handling

* fix(n8n-runner): expose response handling in form

* fix(n8n-runner): preserve async response semantics

---------

Co-authored-by: dadachann <185672915+dadachann@users.noreply.github.com>

src/langbot/pkg/provider/runners/n8nsvapi.py

@@ -39,6 +39,9 @@ class N8nServiceAPIRunner(runner.RequestRunner):
 
         # 获取输出键名，默认为response
         self.output_key = self.pipeline_config['ai']['n8n-service-api'].get('output-key', 'response')
+        self.response_handling = self.pipeline_config['ai']['n8n-service-api'].get('response-handling', 'reply')
+        if self.response_handling not in {'reply', 'ignore'}:
+            raise ValueError(f'Invalid n8n response-handling: {self.response_handling}')
 
         # 获取认证类型，默认为none
         self.auth_type = self.pipeline_config['ai']['n8n-service-api'].get('auth-type', 'none')
@@ -262,7 +265,11 @@ class N8nServiceAPIRunner(runner.RequestRunner):
             async with session.post(
                 self.webhook_url, json=payload, headers=headers, auth=auth, timeout=self.timeout
             ) as response:
-                if response.status != 200:
+                if self.response_handling == 'ignore':
+                    status_ok = 200 <= response.status < 300
+                else:
+                    status_ok = response.status == 200
+                if not status_ok:
                     error_text = (
                         await httpclient.read_limited(
                             response,
@@ -272,6 +279,11 @@ class N8nServiceAPIRunner(runner.RequestRunner):
                     self.ap.logger.error(f'n8n webhook call failed: {response.status}, {error_text}')
                     raise Exception(f'n8n webhook call failed: {response.status}, {error_text}')
 
+                if self.response_handling == 'ignore':
+                    response.release()
+                    self.ap.logger.debug('n8n async webhook accepted; response body ignored')
+                    return
+
                 async for chunk in self._process_response(response):
                     if is_stream:
                         yield chunk