Build and upload Homebrew bottles to GitHub Releases

Parent: #122

Release pipeline builds Homebrew bottles for the agreed macOS matrix and uploads them to GitHub Releases. The tap formula (__M1__) references their SHA256s.

## Definition of done

- Bottles built for: `arm64_sonoma`, `arm64_ventura`, `x86_64_sonoma`, `x86_64_ventura`.
- Bottles uploaded to the GitHub Release for the corresponding stable tag.
- Bottle URLs follow a stable, templatable pattern.
- Formula updater (__M5__) consumes the SHA256s + URLs from the release artifacts.
- Each bottle is `dotnet publish --runtime osx-arm64`/`osx-x64 --self-contained` (or equivalent), notarized per __M3__, then bottled.