The Windows release job hard-failed in run 30125672117: every SignPath
module install attempt got 403 Forbidden from the gallery's OData API,
which is behind Azure Front Door and was also serving 502/504 at the
time. That step was the only hard-fail in an otherwise fail-open signing
chain, so a gallery incident blocked the whole release.
The gallery CDN that serves the nupkg is a separate origin and stayed
healthy throughout, so fall back to a pinned version fetched from it
after the normal install path is exhausted. The fallback verifies a
SHA-256 pin, since that route skips the gallery's own package
validation.
Extracted to a composite action so the release job and the signing
rehearsal cannot drift apart.
Neil
Brennan Benson