Publish a token-free CLI preview artifact for the Homebrew tap

[ChrisonSimtian]

Problem

The Homebrew tap (Fallout-build/homebrew-fallout, #129) has a scaffolded fallout formula but no installable source. Fallout.GlobalTools is public on GitHub Packages, but GitHub's NuGet registry requires auth even for public packages — anonymous download is 401 (authed works; anonymous doesn't). nuget.org has nothing yet (publish waits for the first release/2026 tag). So a public brew install fallout has nowhere token-free to pull from.

Outcome

brew tap Fallout-build/fallout && brew install fallout installs a preview of the CLI on arm64 macOS with no auth — the formula pulls a preview artifact from an anonymously-downloadable source.

Acceptance criteria

• Repeatable way to publish a preview CLI artifact downloadable without auth (e.g. nupkg on a public GitHub Release, or a public preview feed).
• Formula/fallout.rb points at it with real url + sha256; brew install fallout succeeds on arm64 macOS (net10.0 tool on brewed dotnet).
• Refresh story documented: how a new preview updates the formula (relates to Bump tap formula on stable tag + add macOS smoke test #133).

Notes

• arm64-only for now; Intel dropped, revisit on demand.
• Related: Stand up homebrew-fallout tap with initial formula #129 (stand up tap), Bump tap formula on stable tag + add macOS smoke test #133 (bump on tag), As a macOS operator I can install fallout-agent via Homebrew #122 (agent formula).