Covers the full \$B skill list/show/test pipeline against the real
bundled reference skill (defaultTierPaths picks up <repo>/browser-skills/).
Verifies frontmatter shape, the three-tier walk surfaces the bundled
entry, and \$B skill test successfully runs the bundled script.test.ts
in a child bun process.
\$B skill run end-to-end against the live network is intentionally NOT
covered here (would be flaky against news.ycombinator.com); the spawn
lifecycle is exercised in browser-skill-commands.test.ts using inline
synthetic skills.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>