common: clean up failed atomic writes

[GavinnnK]

atomic_write uses delete=False, so an exception from the writer left the partial temp file behind. Always remove it in finally; successful writes still use the same os.replace path.

Adds a regression test for the error path.

Tested on Python 3.12.13. The focused regression, Ruff, py_compile, and git diff --check pass.

[github-actions]

Process replay diff report

Replays driving segments through this PR and compares the behavior to master.
Please review any changes carefully to ensure they are expected.

✅ 0 changed, 66 passed, 0 errors

[GavinnnK]

CI note: the two failing jobs both stop in raylib startup because the external runner is missing libGLESv2.so.2. After rebasing onto current master, build release, build macOS, static analysis, and process replay (0 changed / 66 passed) all pass. No failure reaches the atomic_write change or its regression test.