test(mcp): integration tests for pluggable lifespan wiring

Adds tests/integration/test_main_lifespan.py with 5 cases that exercise
the end-to-end main.app lifespan:

- default (no MCP_SERVICES) mounts both services in BUILTIN order
- MCP_SERVICES=files mounts only files
- MCP_SERVICES='' mounts zero
- MCP_SERVICES=bogus raises RuntimeError at startup
- /health on the root app is unaffected by MCP filtering

Tests use TestClient and mock main.init_mcp_server to record mount
calls, since fastapi-mcp's HTTP endpoints 404 for bare GETs regardless
of mount state (the MCP transport requires an initialize handshake
before any tool call). Mocking avoids that coupling.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

tests/integration/test_main_lifespan.py

@@ -0,0 +1,83 @@
+# coding=utf-8
+"""
+@Time   :2026/6/30
+@Author :tao.chen
+
+End-to-end tests for main.app's lifespan: verify that MCP_SERVICES env
+var correctly gates which services get mounted. Mocks main.init_mcp_server
+to record mount calls rather than relying on fastapi-mcp's HTTP
+response codes (which 404 for bare GETs regardless of mount state
+because the MCP transport requires an initialize handshake first).
+"""
+import pytest
+from fastapi.testclient import TestClient
+
+
+def _get_main_app():
+    """Lazily import main.app so the conftest autouse fixture has run
+    before files_mcp is first imported (via discover_and_filter inside
+    the lifespan)."""
+    import main
+    return main.app
+
+
+@pytest.fixture
+def mock_mount(monkeypatch):
+    """Replace main.init_mcp_server with a recorder.
+
+    Returns a list that gets appended with mount_path each time a
+    service is mounted. The lifespan inside the TestClient context
+    manager triggers all mounts during __enter__.
+    """
+    mounted: list[str] = []
+
+    def fake_init(sub_app):
+        class _FakeMcp:
+            def __init__(self, app):
+                self.app = app
+                self.tools = []
+            def mount_http(self, parent, mount_path):
+                mounted.append(mount_path)
+        return _FakeMcp(sub_app)
+
+    monkeypatch.setattr("main.init_mcp_server", fake_init)
+    return mounted
+
+
+class TestLifespanMounting:
+    def test_default_mounts_both_services(self, monkeypatch, mock_mount):
+        monkeypatch.delenv("MCP_SERVICES", raising=False)
+        with TestClient(_get_main_app()):
+            pass
+        # Both mount paths are present, in BUILTIN_SERVICES order.
+        assert mock_mount == ["/spark-executor-mcp", "/files-mcp"]
+
+    def test_MCP_SERVICES_files_only_mounts_one(self, monkeypatch, mock_mount):
+        monkeypatch.setenv("MCP_SERVICES", "files")
+        with TestClient(_get_main_app()):
+            pass
+        assert mock_mount == ["/files-mcp"]
+
+    def test_MCP_SERVICES_empty_mounts_none(self, monkeypatch, mock_mount):
+        monkeypatch.setenv("MCP_SERVICES", "")
+        with TestClient(_get_main_app()):
+            pass
+        assert mock_mount == []
+
+    def test_MCP_SERVICES_unknown_raises_at_startup(self, monkeypatch, mock_mount):
+        monkeypatch.setenv("MCP_SERVICES", "bogus")
+        with pytest.raises(RuntimeError, match="unknown service names"):
+            with TestClient(_get_main_app()):
+                pass
+        # No mounts attempted
+        assert mock_mount == []
+
+    def test_health_endpoint_unaffected_by_mcp_filtering(self, monkeypatch):
+        # /health is on the root app, independent of MCP service mounting.
+        monkeypatch.delenv("MCP_SERVICES", raising=False)
+        with TestClient(_get_main_app()) as c:
+            assert c.get("/health").status_code == 200
+
+        monkeypatch.setenv("MCP_SERVICES", "")
+        with TestClient(_get_main_app()) as c:
+            assert c.get("/health").status_code == 200