P13: dice — crit/fumble animation + roll visibility

- Crit/fumble emphasis: RollTray (and the Dice page result) highlight a nat-20 /
  critical-success as "✦ Critical ✦" (gold pop + glow) and a nat-1 / critical-
  failure as "✦ Fumble ✦" (red shake). naturalD20() exported from notation.
- DM sees players' rolls: RollFeed now also renders on the Combat page (players'
  rolls already broadcast to the GM).
- Players see the DM's public rolls: new gmRoll message — a hosting GM's rolls
  (Dice page + rollAndShow) broadcast to the table as "GM".
- DM secret-roll toggle (rollStore.secret) on the Dice page suppresses the broadcast.
- Realtime e2e: GM public roll appears in the player's table feed.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/styles/globals.css

@@ -139,3 +139,26 @@ body {
 .animate-dice-rolling {
   animation: dice-shake 0.12s linear infinite;
 }
+
+/* Crit / fumble emphasis on the roll tray */
+@keyframes crit-pop {
+  0% { transform: scale(0.6) rotate(-10deg); }
+  45% { transform: scale(1.2) rotate(5deg); }
+  70% { transform: scale(0.96); }
+  100% { transform: scale(1) rotate(0deg); }
+}
+.animate-crit { animation: crit-pop 0.55s cubic-bezier(0.22, 1, 0.36, 1); }
+@keyframes crit-glow {
+  0%, 100% { box-shadow: 0 0 0 0 rgba(255, 200, 60, 0); }
+  50% { box-shadow: 0 0 24px 5px rgba(255, 200, 60, 0.8); }
+}
+.animate-crit-glow { animation: crit-glow 1s ease-in-out 2; }
+@keyframes fumble-fall {
+  0% { transform: translateY(-5px) rotate(0); }
+  20% { transform: translateX(-7px) rotate(-5deg); }
+  40% { transform: translateX(6px) rotate(4deg); }
+  60% { transform: translateX(-5px) rotate(-3deg); }
+  80% { transform: translateX(3px) rotate(2deg); }
+  100% { transform: translateX(0) rotate(0); }
+}
+.animate-fumble { animation: fumble-fall 0.6s ease-in-out; }