Condense obstacle cards into an overlapping column (v2)

Replace the big-original-card + row-of-minis layout with a single vertical
column: the original sits at the back (accent ring), each play stacks in front
with a heavy negative margin so only its rank+suit peeks out, and the latest
card is fully visible at the bottom. Played cards keep a green/red success ring;
the ChallengePanel's per-play list still credits each player.

Top-aligns the Current Difficulty / Successes boxes so they no longer stretch to
the now-taller card column. Matches the rulebook's column card layout and is far
more compact. Verified in the ChallengePanel, the obstacle list, and on mobile.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/assets/css/scene-play.css

@@ -205,19 +205,40 @@
 .suit-c, .suit-s { border-left: 4px solid var(--suit-black); }
 .suit-h, .suit-d { border-left: 4px solid var(--suit-red); }
 
-.obstacle-card-wrapper {
+/* Overlapping card column for an Obstacle. Cards stack with a heavy negative
+   margin so each earlier card shows only its top strip (rank + suit); the most
+   recent play sits fully visible at the bottom. Rings: accent = the original
+   card, green/red = a play that did / didn't beat the difficulty. */
+.obstacle-stack {
+    --peek: 34px;          /* visible strip of each earlier card */
+    --card-h: 112px;       /* medium card height (card.css) */
+    align-self: start;
     display: flex;
     flex-direction: column;
-    justify-content: center;
     align-items: center;
-    gap: 0.3rem;
+    padding: 2px;          /* room for the rings, which overflow:hidden would clip */
 }
 
-.card-caption {
-    font-size: 0.6rem;
-    text-transform: uppercase;
-    letter-spacing: 0.04em;
-    color: var(--text-muted);
+.stack-card {
+    position: relative;
+    border-radius: var(--radius-sm);
+    line-height: 0;
+}
+
+.stack-card + .stack-card {
+    margin-top: calc(var(--peek) - var(--card-h));
+}
+
+.stack-card.is-original {
+    box-shadow: 0 0 0 2px color-mix(in srgb, var(--accent) 55%, transparent);
+}
+
+.stack-card.is-success {
+    box-shadow: 0 0 0 2px var(--success);
+}
+
+.stack-card.is-failure {
+    box-shadow: 0 0 0 2px var(--danger);
 }
 
 /* Obstacle color (red/black) — fixed by the original card; matching it draws back */
@@ -288,6 +309,7 @@
 }
 
 .obstacle-value-display {
+    align-self: start;
     display: flex;
     flex-direction: column;
     justify-content: center;
@@ -299,6 +321,7 @@
 }
 
 .obstacle-successes-display {
+    align-self: start;
     display: flex;
     flex-direction: column;
     justify-content: center;
@@ -327,26 +350,6 @@
     color: var(--accent);
 }
 
-.played-column {
-    grid-column: 1 / -1;
-    border-top: 1px solid var(--edge-soft);
-    padding-top: 0.75rem;
-    margin-top: 0.5rem;
-}
-
-.played-column h5 {
-    font-size: 0.8rem;
-    color: var(--text-muted);
-    margin-bottom: 0.5rem;
-}
-
-.column-cards-flex {
-    display: flex;
-    flex-wrap: wrap;
-    align-items: center;
-    gap: 0.75rem;
-}
-
 .clear-obstacle-row {
     grid-column: 1 / -1;
 }