Migrate fork-guard tests to pid-cache patch and apply asyncio mark per-method

Two cycle-21 follow-ups in the dbapi tests:

- Fork-guard tests (sync + async) patched
  ``dqlitedbapi.connection.os.getpid`` and
  ``dqlitedbapi.aio.connection.os.getpid``. Cycle 21 moved every
  hot-path pid check to read ``dqliteclient.connection._current_pid``
  via the register_at_fork-refreshed module cache. The
  ``patch("...os.getpid", ...)`` patches were dead code; the tests
  passed only because they also mutated ``_creator_pid`` directly.
  Migrate to patching the cache.

- ``TestAsyncTpcStubs`` carried a class-level
  ``@pytest.mark.asyncio`` decorator but ``test_xid`` is a
  synchronous method. Under pytest-asyncio's strict mode this can
  fail collection. Move the mark from the class to each async
  method individually, matching the sibling
  ``TestAsyncStdlibParityStubs`` class's per-method pattern.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: antoineleclair

tests/aio/test_async_connection_fork_guard.py

@@ -35,7 +35,7 @@ async def test_async_connection_used_after_fork_raises_interface_error() -> None
     conn._creator_pid = fake_parent_pid
 
     with (
-        patch("dqlitedbapi.aio.connection.os.getpid", return_value=fake_parent_pid + 1),
+        patch("dqliteclient.connection._current_pid", fake_parent_pid + 1),
         pytest.raises(InterfaceError, match="fork"),
     ):
         conn._ensure_locks()
@@ -56,7 +56,7 @@ def test_force_close_transport_after_fork_short_circuits() -> None:
     fake_parent_pid = conn._creator_pid + 1
     conn._creator_pid = fake_parent_pid
 
-    with patch("dqlitedbapi.aio.connection.os.getpid", return_value=fake_parent_pid + 1):
+    with patch("dqliteclient.connection._current_pid", fake_parent_pid + 1):
         conn.force_close_transport()
 
     writer.close.assert_not_called()
@@ -82,7 +82,7 @@ async def test_async_connection_close_after_fork_short_circuits() -> None:
     fake_parent_pid = conn._creator_pid + 1
     conn._creator_pid = fake_parent_pid
 
-    with patch("dqlitedbapi.aio.connection.os.getpid", return_value=fake_parent_pid + 1):
+    with patch("dqliteclient.connection._current_pid", fake_parent_pid + 1):
         await conn.close()
 
     inner.close.assert_not_called()

tests/test_connection_after_fork_raises.py

@@ -95,7 +95,7 @@ def test_dbapi_close_after_fork_scrubs_cursors() -> None:
     conn._creator_pid = fake_parent_pid
 
     try:
-        with patch("dqlitedbapi.connection.os.getpid", return_value=fake_parent_pid + 1):
+        with patch("dqliteclient.connection._current_pid", fake_parent_pid + 1):
             conn.close()
 
         assert cursor._closed is True

tests/test_unsupported_method_stubs.py

@@ -103,24 +103,28 @@ def test_create_window_function(self, conn: dqlitedbapi.Connection) -> None:
             conn.create_window_function("name", 0, object)
 
 
-@pytest.mark.asyncio
 class TestAsyncTpcStubs:
+    @pytest.mark.asyncio
     async def test_tpc_begin(self, aconn: AsyncConnection) -> None:
         with pytest.raises(NotSupportedError):
             await aconn.tpc_begin(object())
 
+    @pytest.mark.asyncio
     async def test_tpc_prepare(self, aconn: AsyncConnection) -> None:
         with pytest.raises(NotSupportedError):
             await aconn.tpc_prepare()
 
+    @pytest.mark.asyncio
     async def test_tpc_commit(self, aconn: AsyncConnection) -> None:
         with pytest.raises(NotSupportedError):
             await aconn.tpc_commit()
 
+    @pytest.mark.asyncio
     async def test_tpc_rollback(self, aconn: AsyncConnection) -> None:
         with pytest.raises(NotSupportedError):
             await aconn.tpc_rollback()
 
+    @pytest.mark.asyncio
     async def test_tpc_recover(self, aconn: AsyncConnection) -> None:
         with pytest.raises(NotSupportedError):
             await aconn.tpc_recover()