[Feature] Add Homebrew Cask installation support

[joedlai]

Summary

Publish OpenWorker as a Homebrew Cask so macOS users can install it with:

brew install --cask openworker

If inclusion in Homebrew/homebrew-cask needs more time, an upstream andrewyng/homebrew-tap would provide a useful first step:

brew install --cask andrewyng/tap/openworker

Why

• Gives macOS users a familiar, scriptable installation path.
• Makes setup easier to document and automate.
• Provides standard Homebrew install/uninstall lifecycle behavior.
• Avoids requiring users to download and mount the DMG manually.

Existing release support

The current release workflow already does most of the required packaging work:

• Builds versioned DMGs for Apple Silicon and Intel macOS.
• Publishes both versioned and stable asset names to GitHub Releases.
• Signs and notarizes production macOS builds.
• Packages OpenWorker.app inside the DMG.
• Supports macOS 12 and newer.
• Includes an in-app updater, so the cask should declare auto_updates true.

This should be a cask for the desktop application, not a formula for the Python CLI.

Suggested cask shape

cask "openworker" do
  arch arm: "aarch64", intel: "x86_64"

  version "<latest-version>"
  sha256 arm:   "<arm64-sha256>",
         intel: "<intel-sha256>"

  url "https://github.com/andrewyng/openworker/releases/download/v#{version}/OpenWorker_#{version}_#{arch}.dmg",
      verified: "github.com/andrewyng/openworker/"
  name "OpenWorker"
  desc "Local-first AI coworker for completing everyday tasks"
  homepage "https://openworker.com/"

  livecheck do
    url :url
    strategy :github_latest
  end

  auto_updates true
  depends_on macos: ">= :monterey"

  app "OpenWorker.app"
end

The exact release filenames and checksums should be verified against the latest published release.

Acceptance criteria

• brew install --cask openworker installs the correct architecture when using the official cask, or the documented fully qualified tap command works initially.
• Apple Silicon and Intel downloads both pass checksum and Gatekeeper validation.
• OpenWorker launches successfully after installation.
• brew uninstall --cask openworker removes the application without deleting user data.
• Optional zap behavior is reviewed separately for local state under ~/.config/coworker and only removes it when explicitly requested.
• The README documents the Homebrew installation command.
• Release maintenance is defined, ideally with automation to update the cask version and both SHA-256 checksums after each release.

Validation

Before submission, run the Homebrew cask audit, style, install, launch, and uninstall checks on supported architectures. For the official route, submit the cask to Homebrew/homebrew-cask after confirming its current acceptance requirements.