Animate Try it and Pass exits and deck promotion

Add web/src/discover/motion.ts with the handoff Motion §2, §3, §5 and §6
values over the Web Animations API: the button and Quest log pill bump,
the "Try it!" stamp pop, wiggle and throw right, the Pass page fold with
its shade, the 300 ms deck promotion and the 200 ms reduced-motion fade.
Each exit takes an optional starting transform for the swipe gesture and
returns { finished, cancel }.

DiscoverPage now runs the exit, sends the decision once the card is gone
and keeps input locked until it settles; a refused decision cancels the
exit so the card comes back, and leaving the page mid-exit sends nothing.
The shade uses --color-text (#201e1d).

Maestro task cb7da499-ffda-441d-8574-82e57b332fb6.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

web/src/discover/DiscoverPage.module.css

@@ -206,6 +206,16 @@
   color: var(--color-neutral-900);
 }
 
+/* The shade Pass darkens the card with as it folds. */
+.shade {
+  position: absolute;
+  inset: 0;
+  border-radius: inherit;
+  background: var(--color-text);
+  opacity: 0;
+  pointer-events: none;
+}
+
 /* Pass and Try it: IconButtons with their 11 px labels shown. */
 .actions {
   display: flex;