Plan step 12, containment.md C-03. `selected` was colour alone on a `listitem`, which cannot carry a selected state at all. `<x-list selectable>` (or `selection="single|multi"`) now makes the container a `role="listbox"` and each item an `option` with `aria-selected`; a plain list keeps `role="list"` and marks a selected item `aria-current`. A selected option draws a trailing check as M3's second cue, which `icon-right` replaces. The item reads its list's mode with `@aware`. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01Qwx5USif3wFFmxtHg5U1g9