Add native Windows compatibility

[NicholaiVogel]

Summary

• implement native Windows handle-bound directory and regular-file access with reparse-point rejection
• enable Windows tree copy, managed sync, delete/restore cleanup, no-replace installation, and identity-checked directory replacement rollback
• implement Windows config publication and harden Windows state-lock file access
• add hosted windows-latest Rust/Bun integration CI and select .exe test binaries
• document the supported Windows runtime surface and validation limits

Validation

• git diff --check
• bun x tsc --noEmit
• bun test tests/npm_launcher.test.ts
• hosted windows-latest workflow added and will provide the authoritative Rust compile/runtime result

The local checkout does not have cargo/rustc, so native Windows compilation cannot be run locally.