Adapt POSIX mmap implementation for Windows

[lnfjpt]

As titled.

[github-actions]

🤖 Auto-triage suggestion: this looks like a sub-issue of #272 — Refine checkpoint mechanism (confidence: high).

Reason: The issue is about adapting the mmap implementation for Windows, which falls under the persistence layer and mmap behavior tracked by #272.

Auto-applied: labels → store

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