Windows fs built-in (CI run only)

[basal-alfonso]

Draft to run the Windows CI job on the Windows fs built-in. Not for merge as-is.

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Summary by cubic

Adds a Windows-specific implementation of the fs built-in so the Windows CI job can run it. This draft is for CI validation only, not intended for merge.

Details

• Windows implementation enforces raw-spelling grammar, reparse point denial, and POSIX-style temp-and-rename replacement.
• Unix-only code in fs.rs and the affected test are now gated behind #[cfg(unix)].

^{Written for commit 76b9008. Summary will update on new commits.}