refactor: root release config in gateway runtime (#2611)

Co-authored-by: greatmengqi <chenmengqi.0376@bytedance.com>

backend/tests/test_gateway_deps_config.py

@@ -0,0 +1,41 @@
+from __future__ import annotations
+
+from fastapi import Depends, FastAPI
+from fastapi.testclient import TestClient
+
+from app.gateway.deps import get_config
+from deerflow.config.app_config import AppConfig
+from deerflow.config.sandbox_config import SandboxConfig
+
+
+def test_get_config_returns_app_state_config():
+    """get_config should return the exact AppConfig stored on app.state."""
+    app = FastAPI()
+    config = AppConfig(sandbox=SandboxConfig(use="test"))
+    app.state.config = config
+
+    @app.get("/probe")
+    def probe(cfg: AppConfig = Depends(get_config)):
+        return {"same_identity": cfg is config, "log_level": cfg.log_level}
+
+    client = TestClient(app)
+    response = client.get("/probe")
+
+    assert response.status_code == 200
+    assert response.json() == {"same_identity": True, "log_level": "info"}
+
+
+def test_get_config_reads_updated_app_state():
+    """Swapping app.state.config should be visible to the dependency."""
+    app = FastAPI()
+    app.state.config = AppConfig(sandbox=SandboxConfig(use="test"), log_level="info")
+
+    @app.get("/log-level")
+    def log_level(cfg: AppConfig = Depends(get_config)):
+        return {"level": cfg.log_level}
+
+    client = TestClient(app)
+    assert client.get("/log-level").json() == {"level": "info"}
+
+    app.state.config = app.state.config.model_copy(update={"log_level": "debug"})
+    assert client.get("/log-level").json() == {"level": "debug"}