solitaire: let cards be dragged, not only tapped

Tapping stays exactly as it was. A press that travels more than a few
pixels becomes a drag instead, and both paths go through the same pick()
and accepts(), so what lights up and what a move means never depends on
how you did it. The run follows the pointer as a copy while the real
cards stay on the felt, faded, and letting go over nothing keeps the run
in your hand with the targets still lit.

Capture happens when the press becomes a drag, not on pointerdown:
capturing early retargets the click that a tap ends with, and tapping
quietly stops working.

internal/web/templates/solitaire.html

@@ -96,7 +96,7 @@
       </button>
 
       <p class="text-xs text-[color:var(--ink)]/45">
-        Click a card, then where it goes. Double-click sends it home.
+        Drag a card where it goes, or click it and then click the spot. Double-click sends it home.
       </p>
 
       <button type="button" data-cash