Add Homebrew distribution support for Seam CLI

[razor-x]

Summary

This PR adds Homebrew as a distribution channel for the Seam CLI, enabling macOS and Linux users to install the tool via brew install seam.

Key Changes

• Automated Homebrew formula updates: Added a new homebrew job in the publish workflow that automatically bumps the Homebrew formula in homebrew-core on each release
  • Waits for the npm package to be published before attempting the formula bump
  • Uses brew bump-formula-pr to create pull requests with updated URL and SHA256
  • Configured to only run on stable releases (excludes pre-release versions with - in the tag)
• Reference formula: Added .github/homebrew/seam.rb as a reference copy of the Homebrew formula that lives in homebrew-core
  • Includes installation via npm with proper symlink setup
  • Includes basic test coverage for version output and authentication check
• Documentation: Updated README.md to document Homebrew as an installation method alongside npm and AUR

Implementation Details

• The workflow job depends on the npm job completing successfully before attempting the Homebrew formula bump
• The formula bump uses git credentials from secrets (GH_TOKEN, GIT_USER_NAME, GIT_USER_EMAIL) for authentication
• The tarball URL is automatically computed from the scoped package name, handling the scope-to-filename conversion correctly
• SHA256 validation is delegated to homebrew-core's pull request checks via the --no-audit flag

https://claude.ai/code/session_0144M6JQSTdYRxdw7FNsnDcN