chore: remove standalone LangGraph Server remnants from agent docs (#3304) (#3671)

Follow-up to #3301 / #3344. The Gateway-embedded runtime is the standard
topology — there is no standalone LangGraph service — but two stale
references slipped past the cleanup guard:

- .github/copilot-instructions.md still told contributors that `make dev`
  "Starts LangGraph (2024)" and wrote logs/langgraph.log.
- SandboxAuditMiddleware's docstring pointed audit logs at langgraph.log.

Update both to the Gateway-embedded reality (gateway.log) and extend
test_gateway_runtime_cleanup.py to pin the agent-instruction docs so the
standalone references can't reappear.

Stays within the safe scope of #3304: does not touch langgraph_auth.py,
langgraph.json, or the langgraph-api / langgraph-cli / langgraph-runtime-inmem
deps, which the issue gates on maintainer confirmation of Studio / direct
LangGraph Server support.

.github/copilot-instructions.md

@@ -94,9 +94,9 @@ make dev
 Behavior:
 
 - Stops existing local services first.
-- Starts LangGraph (`2024`), Gateway (`8001`), Frontend (`3000`), nginx (`2026`).
+- Starts Gateway (`8001`, with the embedded LangGraph-compatible runtime), Frontend (`3000`), nginx (`2026`). There is no standalone LangGraph service.
 - Unified app endpoint: `http://localhost:2026`.
-- Logs: `logs/langgraph.log`, `logs/gateway.log`, `logs/frontend.log`, `logs/nginx.log`.
+- Logs: `logs/gateway.log`, `logs/frontend.log`, `logs/nginx.log`.
 
 Stop services:
 

backend/packages/harness/deerflow/agents/middlewares/sandbox_audit_middleware.py

@@ -201,7 +201,7 @@ class SandboxAuditMiddleware(AgentMiddleware[ThreadState]):
     1. **Command classification**: regex + shlex analysis grades commands as
        high-risk (block), medium-risk (warn), or safe (pass).
     2. **Audit log**: every bash call is recorded as a structured JSON entry
-       via the standard logger (visible in langgraph.log).
+       via the standard logger (visible in gateway.log).
 
     High-risk commands (e.g. ``rm -rf /``, ``curl url | bash``) are blocked:
     the handler is not called and an error ``ToolMessage`` is returned so the

backend/tests/test_gateway_runtime_cleanup.py

@@ -147,3 +147,14 @@ def test_gateway_runtime_docs_do_not_reference_transition_modes():
         assert "./scripts/deploy.sh --gateway" not in content, path
         assert "docker compose --profile gateway" not in content, path
         assert "`/api/langgraph/*` → LangGraph" not in content, path
+
+
+def test_agent_instruction_docs_do_not_reference_standalone_langgraph_server():
+    """Agent/Copilot instruction docs must describe only the Gateway-embedded
+    runtime — no standalone LangGraph service, port 2024, or langgraph.log."""
+    content = _read(".github/copilot-instructions.md")
+
+    assert "langgraph.log" not in content
+    assert "localhost:2024" not in content
+    assert "127.0.0.1:2024" not in content
+    assert "Starts LangGraph" not in content