As a macOS user I can install the fallout CLI via Homebrew

[ChrisonSimtian]

Problem

No first-class way to install the fallout CLI (the .NET global tool Fallout.GlobalTools, command fallout — src/Fallout.Cli) on macOS. The tap (Fallout-build/homebrew-fallout) exists with a scaffolded fallout formula, but it's on placeholders with no anonymous source to install from (#482). This is the CLI counterpart to the agent story #122.

Outcome

brew tap Fallout-build/fallout && brew install fallout installs the CLI on arm64 macOS with no auth and brew-managed upgrades. Formula installs via depends_on "dotnet" + dotnet tool install (not a self-contained binary).

Acceptance criteria

• Publish a token-free CLI preview artifact for the Homebrew tap #482 done — a token-free preview artifact exists.
• Formula/fallout.rb uses a real url + sha256; brew install fallout succeeds on arm64 macOS (net10.0 tool on brewed dotnet).
• Refresh/bump story documented (relates to Bump tap formula on stable tag + add macOS smoke test #133).

Notes

• Preview is enough to close this; GA can follow later.
• arm64-only for now; Intel dropped, revisit on demand.
• Part of [Epic] Distribute Fallout via native package managers (winget, Homebrew, .deb) #139. Related: As a macOS operator I can install fallout-agent via Homebrew #122 (agent sibling), Publish a token-free CLI preview artifact for the Homebrew tap #482, Stand up homebrew-fallout tap with initial formula #129, Bump tap formula on stable tag + add macOS smoke test #133.