Add Windows ARM64 cross-compiled archive path

[starr-openai]

Summary

• add the Windows ARM64 nextest archive path: build once on x64 Windows, then run ARM64 shards from the uploaded archive
• set up the Windows MSVC ARM64 environment before producing that archive
• prefer lld/rust-lld via a small wrapper for the ARM64 archive link path
• create the archive extract directory before shard extraction

Validation

• current-head ARM64 archive probe: https://github.com/openai/codex/actions/runs/25890163429
• on 8718dfc9d9ddfd911a5fae2d57159e26ed606f4b, Build Windows arm64 nextest archive and all four Windows ARM64 archive shards succeeded
• archive producer wall time was 14m08s; archive shard times were 7m07s, 5m33s, 6m18s, and 7m26s

Notes

• this PR is stacked on starr/windows-ci-arm64-shards-4-full-ci
• the manual full probe still has unrelated Linux test failures outside the Windows ARM64 archive path