Add the fullscript-claude-code formula

[lugray]

Migrate https://git.fullscript.io/devops/rx-workflows/claude-code-setup to a homebrew cask. Notably, instead of merging our settings into the user's settings, we put them in /Library/Application Support/ClaudeCode/managed-setting.json, the place anthropic recommends for managed settings.

Testing - will not work until rx is released with the new --json flag

• cd /opt/homebrew/Library/Taps/fullscript/homebrew-tools
• git fetch
• git checkout fullscript-claude-code
• brew install --cask fullscript/tools/fullscript-claude-code

[RyanBrushett]

Tested with the prerelease version of rx that has the --json flag. Looks nice! Works nicely, I'd say.

• It needs the password to write the managed settings file. This is probably a non-issue? Users likely won't be running this themselves. Could we get the daemon process to elevate privileges when it needs it like that?
• Uninstalling didn't remove the claude-code cask. This might not matter either since we'll be managing it and can always just remove both.