Agent Skills: gtm-performance-audit

Automatically audit Google Tag Manager implementations for performance impact when user mentions GTM, tag manager, tracking tags, marketing tags, or asks about tag performance. Analyzes container configuration, measures tag execution timing, identifies blocking tags, audits custom HTML safety, evaluates trigger efficiency, and maps tag impact to Core Web Vitals. Invoke when user says "GTM is slow", "too many tags", "tag manager performance", "tracking tags impact", or asks about marketing tag overhead.