Replace pytest-retry with pytest-rerunfailures for Windows stability

Windows CI was experiencing worker crashes due to ConnectionResetError in
pytest-retry's internal server when running with pytest-xdist:

```
pytest_retry\server.py", line 45, in run_server
    chunk = conn.recv(4096)
ConnectionResetError: [WinError 10054] An existing connection was forcibly
closed by the remote host
```

This crashed worker gw0, leaving orphaned temp directories with locked
SQLite files, causing cascading teardown failures in caching tests.

Even pytest-retry 1.7.0 (latest, with socket cleanup fixes) has unresolved
race conditions in its server/client communication on Windows with xdist.

**Solution**: Switch to pytest-rerunfailures, which has better pytest-xdist
compatibility and is the officially recommended plugin by pytest-dev.

**Changes**:
- Replace `pytest-retry>=1.7.0` with `pytest-rerunfailures>=14.0`
- Update flaky test markers:
  - `@pytest.mark.flaky(retries=N)` → `@pytest.mark.flaky(reruns=N)`
  - `delay=N` → `reruns_delay=N`
- Updated 3 flaky tests:
  - `test_github_mcp_remote.py::TestGithubMCPRemote` (network tests)
  - `test_mcp_config.py::test_multi_client_transform_with_filtering` (subprocess timing)
  - `test_openapi_experimental.py::test_client_headers_proxy` (proxy test)

pytest-rerunfailures is actively maintained by pytest-dev and explicitly
documents compatibility with pytest-xdist, including support for rerunning
tests when workers crash.

Related: https://github.com/jlowin/fastmcp/actions/runs/19540316503/job/55944598449

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

Author: chrisguidry

pyproject.toml

@@ -70,7 +70,7 @@ dev = [
     "pytest-flakefinder>=1.1.0",
     "pytest-httpx>=0.35.0",
     "pytest-report>=0.2.1",
-    "pytest-retry>=1.7.0",
+    "pytest-rerunfailures>=14.0",
     "pytest-timeout>=2.4.0",
     "pytest-xdist>=3.6.1",
     "ruff>=0.12.8",

tests/client/test_openapi_experimental.py

@@ -183,7 +183,7 @@ async def test_client_with_excluded_header_is_ignored(sse_server: str):
         assert headers["host"] == "fastapi"
 
 
-@pytest.mark.flaky(retries=2, delay=1)
+@pytest.mark.flaky(reruns=2, reruns_delay=1)
 async def test_client_headers_proxy(proxy_server: str):
     """
     Test that client headers are passed through the proxy to the remove server.

tests/integration_tests/test_github_mcp_remote.py

@@ -34,7 +34,7 @@ def fixture_streamable_http_client() -> Client[StreamableHttpTransport]:
     )
 
 
-@pytest.mark.flaky(retries=2, delay=1)
+@pytest.mark.flaky(reruns=2, reruns_delay=1)
 class TestGithubMCPRemote:
     async def test_connect_disconnect(
         self,

tests/test_mcp_config.py

@@ -639,7 +639,7 @@ def add(a: int, b: int) -> int:
         assert "test_1_transformed_add" not in tools_by_name
 
 
-@pytest.mark.flaky(retries=3)
+@pytest.mark.flaky(reruns=3)
 async def test_multi_client_transform_with_filtering(tmp_path: Path):
     """
     Tests that tag-based filtering works when using a transforming MCPConfig.