fix: _build_ctx补pipeline_id字段，修复/help列不出产线命令

pipeline_service/agent_loop_v2.py

@@ -559,10 +559,11 @@ class AgentExecutor:
         return f"未知工具: {tool_name}"
 
     def _build_ctx(self) -> dict:
-        """构造传给产线能力 handler 的上下文。"""
+        """构造传给产线能力 handler / slash 命令的上下文。"""
         return {
             "project_id": self.project_id,
             "user_id": self.user_id,
+            "pipeline_id": self.pipeline_id,
             "workspace_dir": self.workspace_dir,
             "model_name": self.model_name,
             "config": self.config,