feat: Add command auto-completion generation for brew formula

[DylanDevelops]

Update .goreleaser.yml to invoke generate_completions_from_executable in the brew install stanza so the Homebrew formula will generate shell completions from the tmpo executable on install. Existing install and test steps are preserved.

Pull Request Checklist

• I have read and followed the contribution guidelines.
• My pull request targets the main branch of tmpo.
• I have tested these changes locally on my machine.

Description

This pull request makes a small but useful enhancement to the Homebrew formula configuration by adding shell completions generation for the tmpo executable. This will improve the user experience by enabling command-line autocompletion for users who install via Homebrew.