fix(tabletop): tilt cards uniformly about the y axis

Apply the same tilt to every stacked part and rotate it about its local
Y axis instead of Z. Default tilt to 1 degree when a stacking strategy
is present, and arc the poker deck along the surface's bottom edge.

packages/tabletop/src/stacking.ts

@@ -43,9 +43,10 @@ export function stackingOffset(
   const shownIndex = shown.indexOf(index);
   if (shownIndex < 0) return NO_OFFSET;
 
-  // `tilt` fans each shown part about its local Y (long) axis, so the stack's
-  // edges stay visible. It applies even without a curve.
-  const tilt = (stacking?.tilt ?? 0) * shownIndex;
+  // `tilt` rotates each shown part about its local Y (long) axis by the same
+  // amount. It applies even without a curve. Defaults to 1° when a stacking
+  // strategy is present but doesn't specify a tilt.
+  const tilt = stacking?.tilt ?? (stacking ? 1 : 0);
 
   // The horizontal position along the curve (or a straight pile when there's
   // no curve), plus the normalized progress used to ramp the z height.