feat(trace):LangGraph -> lead_agent and set custom agent_name to run_name (#3101)

* feat(trace):LangGraph -> lead_agent and set user custom agent name to run_name

* feat(trace):follow github copilot suggest

* feat(trace):Refactor run_name resolution and improve test coverage

backend/packages/harness/deerflow/runtime/runs/naming.py

@@ -0,0 +1,16 @@
+"""Run naming helpers for LangChain/LangSmith tracing."""
+
+from __future__ import annotations
+
+from collections.abc import Mapping
+from typing import Any
+
+
+def resolve_root_run_name(config: Mapping[str, Any], assistant_id: str | None) -> str:
+    for container_name in ("context", "configurable"):
+        container = config.get(container_name)
+        if isinstance(container, Mapping):
+            agent_name = container.get("agent_name")
+            if isinstance(agent_name, str) and agent_name.strip():
+                return agent_name
+    return assistant_id or "lead_agent"