Store.save renames the tempfile while it is still open — crashes on Windows with WinError 32

[Proteus7]

Thanks for the tool — the incremental sync design is genuinely nice. Two environment reports incoming; this one is Windows.

Environment: claude-backup 0.1.12 (commit 6c009ec), Python 3.13, Windows 11, installed via uv tool install.

Symptom: every run crashes on the first write:

  File "...\claude_backup\__init__.py", line 238, in save
    Path(f.name).rename(cache_file)
...
PermissionError: [WinError 32] The process cannot access the file because it is being used by another process: '...\\account.json-ifkiygrk'

Cause: in Store.save, the Path(f.name).rename(cache_file) happens inside the with NamedTemporaryFile(...) block, while the handle is still open. POSIX allows renaming an open file; Windows does not. The except BaseException cleanup path then also fails for the same reason (unlink of an open file).

Suggested fix: keep delete=False, write + flush inside the block, and move the rename to after the with closes the handle — os.replace(f.name, cache_file) after the block preserves the atomic-replace semantics on both platforms (Path.rename refuses to overwrite an existing target on Windows too, so os.replace covers that case as well).

Happy to test a fix — I have a Windows + WSL setup where this reproduces 100% of the time.