<x-card> always titled itself with an <h3>, so a card straight under a page's <h1> skipped a level, which SealShare's download page did with no way round it from the application. `heading` takes h2 to h6, or div or p for a title that is not a heading, as <x-pane> and <x-app-bar> already do; h3 stays the default. The skill also says a card holds one subject, as M3 does (plan step 46). Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>