feat: automate Homebrew tap updates on release

[kevinquillen]

Summary

Automates Homebrew tap updates on release, matching the pattern used in Auryn. Merged with #40 (install script and README installation docs).

Changes

publish-homebrew job (.github/workflows/release.yml)

• Runs after release assets are uploaded
• Downloads the four *.tar.gz.sha256 files from the GitHub release
• Renders packaging/homebrew/hoi.rb with the new version and checksums
• Commits and pushes Formula/hoi.rb to homebrew-tap
• Skips tags containing a hyphen (prereleases), same as Auryn

packaging/homebrew/hoi.rb

• Formula template with REPLACE_WITH_* checksum placeholders (replaces the hardcoded 0.7.1 copy from feat: add binary install script and installation docs #40)

CONTRIBUTING.md

• Documents automated tap updates and HOMEBREW_TAP_TOKEN (replaces manual step 6 from feat: add binary install script and installation docs #40)

Also includes from #40: scripts/install.sh, README installation section.

Prerequisites

Ensure the hoi repo has a HOMEBREW_TAP_TOKEN secret with write access to kevinquillen/homebrew-tap.

Test plan

• Merge and tag a patch release (e.g. v0.7.2) to verify publish-homebrew updates homebrew-tap
• Confirm brew install kevinquillen/tap/hoi serves the new version