Plan step 38: the shadow-level grid moves onto <x-surface> and
<x-grid>; each tile is a data-md-showcase-elevation-tile keyed on
data-md-elevation, drawing var(--md-sys-elevation-1..5) — the same
tokens the label now names instead of the retired shadow-elevation-*
utility.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Qwx5USif3wFFmxtHg5U1g9