Plan step 36, navigation review sweep. <x-list-detail> renders an <x-button> as the single-pane back action, but only pane.css picked up button.css when the carry-over landed; an application importing layout/list-detail.css alone got an unstyled back button. A new check reads every layout view's component tags against its stylesheet's imports, as the group stylesheet tests do for components. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01Qwx5USif3wFFmxtHg5U1g9