test: add tests for /health/detailed endpoint and gateway health probe

- TestHealthDetailedEndpoint: 3 tests for the new API server endpoint
  (returns runtime data, handles missing status, no auth required)
- TestProbeGatewayHealth: 5 tests for _probe_gateway_health()
  (URL normalization, successful/failed probes, fallback chain)
- TestStatusRemoteGateway: 4 tests for /api/status remote fallback
  (remote probe triggers, skipped when local PID found, null PID handling)

tests/gateway/test_api_server.py

@@ -220,6 +220,7 @@ def _create_app(adapter: APIServerAdapter) -> web.Application:
     app = web.Application(middlewares=mws)
     app["api_server_adapter"] = adapter
     app.router.add_get("/health", adapter._handle_health)
+    app.router.add_get("/health/detailed", adapter._handle_health_detailed)
     app.router.add_get("/v1/health", adapter._handle_health)
     app.router.add_get("/v1/models", adapter._handle_models)
     app.router.add_post("/v1/chat/completions", adapter._handle_chat_completions)
@@ -277,6 +278,58 @@ class TestHealthEndpoint:
             assert data["platform"] == "hermes-agent"
 
 
+# ---------------------------------------------------------------------------
+# /health/detailed endpoint
+# ---------------------------------------------------------------------------
+
+
+class TestHealthDetailedEndpoint:
+    @pytest.mark.asyncio
+    async def test_health_detailed_returns_ok(self, adapter):
+        """GET /health/detailed returns status, platform, and runtime fields."""
+        app = _create_app(adapter)
+        with patch("gateway.status.read_runtime_status", return_value={
+            "gateway_state": "running",
+            "platforms": {"telegram": {"state": "connected"}},
+            "active_agents": 2,
+            "exit_reason": None,
+            "updated_at": "2026-04-14T00:00:00Z",
+        }):
+            async with TestClient(TestServer(app)) as cli:
+                resp = await cli.get("/health/detailed")
+                assert resp.status == 200
+                data = await resp.json()
+                assert data["status"] == "ok"
+                assert data["platform"] == "hermes-agent"
+                assert data["gateway_state"] == "running"
+                assert data["platforms"] == {"telegram": {"state": "connected"}}
+                assert data["active_agents"] == 2
+                assert isinstance(data["pid"], int)
+                assert "updated_at" in data
+
+    @pytest.mark.asyncio
+    async def test_health_detailed_no_runtime_status(self, adapter):
+        """When gateway_state.json is missing, fields are None."""
+        app = _create_app(adapter)
+        with patch("gateway.status.read_runtime_status", return_value=None):
+            async with TestClient(TestServer(app)) as cli:
+                resp = await cli.get("/health/detailed")
+                assert resp.status == 200
+                data = await resp.json()
+                assert data["status"] == "ok"
+                assert data["gateway_state"] is None
+                assert data["platforms"] == {}
+
+    @pytest.mark.asyncio
+    async def test_health_detailed_does_not_require_auth(self, auth_adapter):
+        """Health detailed endpoint should be accessible without auth, like /health."""
+        app = _create_app(auth_adapter)
+        with patch("gateway.status.read_runtime_status", return_value=None):
+            async with TestClient(TestServer(app)) as cli:
+                resp = await cli.get("/health/detailed")
+                assert resp.status == 200
+
+
 # ---------------------------------------------------------------------------
 # /v1/models endpoint
 # ---------------------------------------------------------------------------