feat: add Homebrew cask distribution

[NormallyGaussian]

Summary

• Adds Homebrew tap support: brew install parallel-web/tap/parallel-cli
• Cask template at homebrew/parallel-cli.rb with quarantine stripping (no Apple Developer account needed)
• Script (scripts/update-homebrew-formula.py) generates cask with real SHA256 checksums from GitHub releases
• publish-homebrew job in release.yml auto-updates the tap on stable releases (skips RCs)
• README and MAINTAINERS.md updated

Tested locally against v0.1.2 — fresh download, install, version check, and live API call all passed with no Gatekeeper popup.

Steps to activate

1. Create the tap repo

Create parallel-web/homebrew-tap on GitHub:

• Public repo
• Initialize with a README (so it has a main branch)
• Add a Casks/ directory with an initial parallel-cli.rb (the CI will overwrite it on first release, or you can seed it manually — see step 3)

2. Add the HOMEBREW_TAP_TOKEN secret

Create a GitHub fine-grained PAT (or classic PAT with repo scope) that has write access to parallel-web/homebrew-tap.

Then add it as a secret in this repo (parallel-web/parallel-web-tools):

• Go to Settings → Secrets and variables → Actions
• Add HOMEBREW_TAP_TOKEN with the PAT value

3. Seed the tap with v0.1.2 (optional)

To make Homebrew work before the next release, generate and push the cask for the current release:

# Generate cask with real checksums from v0.1.2
uv run python scripts/update-homebrew-formula.py --version 0.1.2 --output /tmp/parallel-cli.rb

# Clone the tap repo and add the cask
git clone git@github.com:parallel-web/homebrew-tap.git /tmp/homebrew-tap
mkdir -p /tmp/homebrew-tap/Casks
cp /tmp/parallel-cli.rb /tmp/homebrew-tap/Casks/parallel-cli.rb
cd /tmp/homebrew-tap
git add -A && git commit -m "Add parallel-cli cask v0.1.2" && git push

4. Verify

brew install parallel-web/tap/parallel-cli
parallel-cli --version

After this, every future stable release will automatically update the cask in the tap.

Test plan

• Generated cask with real v0.1.2 checksums
• Installed via local Homebrew tap — clean install, no warnings
• No Gatekeeper popup (quarantine stripped in preflight)
• parallel-cli --version returns 0.1.2
• parallel-cli search works end-to-end
• Uninstall/reinstall cycle clean
• CI: publish-homebrew job runs on next stable release