feat(commands): add mas completions

[yoktur]

Adds completions for the third-party mas CLI.

• registers the current commands and documented aliases
• suggests installed App Store app IDs and names where applicable
• removes the version column from installed-app descriptions
• adds the Nerd Fonts App Store icon

The generator reuses the existing package-manager implementation and runs mas list directly, without adding caching or dependencies.

Tested against mas 7.0.0 on macOS. Targeted race tests, just lint, go vet ./..., and the build pass.

The full test suite also reaches unrelated failures in the existing long-command TUI tests.