Draw M3's dragged state on a card

Plan step 23, containment.md § Missing ("Cards: the dragged state").
`data-dragged` on `<x-card>` takes the top of M3's card elevation scale
— Level4 (8dp) elevated, Level3 (6dp) filled and outlined — under the
16% dragged state layer from tokens/state.css. The row's hover and press
rules now exclude a dragged card, so the card a pointer is holding stays
at its dragged level. The application owns the attribute: nothing in the
browser tells a card it is being carried.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Qwx5USif3wFFmxtHg5U1g9

resources/boost/skills/livewire-material-development/SKILL.md

@@ -432,6 +432,8 @@ A card or list item that opens something is a **row**: `data-list-row` on it and
 </x-card>
 ```
 
+`data-dragged` on the card draws M3's dragged state — elevation 8dp elevated / 6dp filled and outlined, under the 16% dragged state layer. The application sets it when its drag starts and removes it on drop; pair any drag with a single-pointer alternative (a menu with the same actions), as M3 requires.
+
 That is M3's *non-actionable card with actionable elements*: Tab walks the controls inside. For M3's *directly actionable card*, where Tab lands on the card and then moves to the next card, add `actionable` (and `role="link"` where it goes somewhere) and put `tabindex="-1"` on the opener — the card is then the tab stop, named by its `title`, and Enter or Space on it reaches the opener while the card's other actions follow it.
 
 ### `<x-list>`, `<x-list-item>`