Fix tests on Windows

[vgreg]

It seems that the tests are not working properly on Windows. We should confirm the issue and fix the tests so that they work on all major platforms.

[jevwithwind]

Hi! I'm doing similar work with limit order book data on the JPX side (master's research) with a Windows PC, and recently stumbled across MeatPy. This issue looked like something I could help with, so I dug into the failures — here's the diagnosis, in case it's useful.

Reproduced on Windows 11 (current main): 38 failures, all in test code — the library itself is Windows-clean.

Two root causes, both in how the tests manage temp files:

1. 36 tests hold a tempfile.NamedTemporaryFile(delete=False) handle open for the whole test body and call Path(tmp.name).unlink() inside the with block. POSIX allows unlinking an open file; Windows raises PermissionError (WinError 32). Affects test_csv_writer.py, test_parquet_writer.py, test_writers.py, test_recorders.py.
2. The two test_itch50_reader_writer.py failures use the default delete=True, which on Windows opens the file with O_TEMPORARY — so ITCH50Writer's own re-open of the same path (itch50_writer.py:81) fails with Errno 13 at flush.

The writers themselves are fine — every library-side open is context-scoped, so no product code needs to change.

I have a minimal fix passing the full suite locally (659 passed; ruff clean): converting the five affected test files to pytest's tmp_path fixture, which removes the manual cleanup entirely and behaves identically on Linux. Happy to open a PR if that's useful, or leave the diagnosis here if you'd rather take it yourself.

Two smaller things I noticed and left alone: test_itch2_reader.py uses the same idiom (it passes, but leaks temp files since it never unlinks), and a windows-latest leg in test.yml would lock the fix in. Glad to fold either into the PR or a follow-up.