Clarify stdio coverage comments

Author: Kludex

tests/interaction/transports/_stdio_server.py

@@ -60,7 +60,7 @@ async def main() -> None:
     # Save subprocess coverage before the marker so forced teardown cannot lose it.
     cov = getattr(coverage.process_startup, "coverage", None)
     if cov is not None:  # pragma: no branch
-        # Stop tracing before the final save.
+        # Leave nothing for coverage's atexit hook to rewrite if teardown is interrupted.
         cov.stop()
         cov.save()  # pragma: lax no cover - untraced: stop() above already ended measurement
     # The test uses this marker to distinguish clean exit from termination.

tests/interaction/transports/test_stdio.py

@@ -58,7 +58,7 @@ async def collect(params: LoggingMessageNotificationParams) -> None:
                 command=sys.executable,
                 args=["-m", _stdio_server.__name__],
                 cwd=str(_REPO_ROOT),
-                # Preserve subprocess coverage and suppress an AnyIO 3.14 import warning.
+                # Preserve subprocess coverage and suppress anyio's `SyntaxWarning` on Python 3.14.
                 env={key: value for key, value in os.environ.items() if key.startswith("COVERAGE_")}
                 | {"PYTHONWARNINGS": "ignore::SyntaxWarning"},
             ),