games: burial send-offs, money rain on wins, and honest stack targeting

Three front-end changes to the casino games:

- uno: a draw-card stack now names the seat it's actually pointed at
  ("+N on Beep") instead of always reading "+N on you". The bill reads
  v.turn, which the engine advances to the target when a draw card lands.

- uno: the No Mercy rule buries a seat with some ceremony now. bury()
  rolls one of four send-offs over the seat (or your hand, if it's you) —
  a rockslide that piles up, a tombstone, a coffin, or the Mega Man death
  burst — each with its own synth sound, and a static headstone under
  reduced motion. The "Buried on N" badge still rides alongside.

- all games: winning makes it rain. FX.moneyRain drops a curtain of bills
  and coins with a jackpot coin-cascade sound, gated by significance so it
  reads as a win and not as noise: hold'em keeps its light per-pot confetti
  and only rains on a real haul (>= 20bb), while the confetti stays the
  rare cherry (natural 21, full board clear, phrase solved outright).

internal/web/static/js/casino-fx.js

@@ -319,6 +319,65 @@
     return Promise.all(done);
   }
 
+  // moneyRain: it rains money. The big finish on a win — bills and coins tumbling
+  // the whole height of the window, swaying and spinning as they fall. Louder than
+  // confetti, and it carries its own sound (a coin cascade) so it can stand in for
+  // the plain win fanfare wherever a table decides a win is worth the theatre.
+  //
+  // Like burst, the sound comes before the reduced-motion bail: no rain still
+  // deserves to be heard.
+  function moneyRain(opts) {
+    opts = opts || {};
+    if (opts.sound !== false) sfx(opts.sound || "jackpot");
+    if (reduced) return Promise.resolve();
+
+    var n = opts.count || 22;
+    var glyphs = opts.glyphs || ["💶", "💰", "🪙", "💵", "💴", "🤑"];
+    var vw = window.innerWidth || document.documentElement.clientWidth;
+    var vh = window.innerHeight || document.documentElement.clientHeight;
+    var done = [];
+
+    for (var i = 0; i < n; i++) {
+      var bit = document.createElement("div");
+      bit.className = "pete-money";
+      bit.textContent = glyphs[i % glyphs.length];
+      stage().appendChild(bit);
+
+      // Spread across the width in even lanes, each nudged off its lane so the
+      // curtain doesn't read as a grid. It sways sideways and spins on the way down.
+      var x = ((i + 0.5) / n) * vw + jitter(i, vw / n / 2);
+      var drift = jitter(i + 5, 80);
+      var startY = -50 - Math.abs(jitter(i + 2, 180));
+      var spin = jitter(i, 300);
+      var scale = 0.85 + Math.abs(jitter(i + 3, 0.55));
+
+      done.push(
+        bit
+          .animate(
+            [
+              { transform: t(x, startY, scale, 0), opacity: 0, offset: 0 },
+              { transform: t(x + drift, startY + 40, scale, spin * 0.2), opacity: 1, offset: 0.1 },
+              { transform: t(x - drift, vh * 0.55, scale, spin * 0.6), opacity: 1, offset: 0.6 },
+              { transform: t(x + drift * 0.5, vh + 60, scale, spin), opacity: 1, offset: 1 },
+            ],
+            {
+              duration: 1600 + Math.abs(jitter(i + 9, 1)) * 900,
+              easing: "cubic-bezier(0.35, 0.15, 0.55, 1)",
+              fill: "both",
+              delay: Math.abs(jitter(i, 320)),
+            }
+          )
+          .finished.catch(function () {})
+          .then(
+            (function (b) {
+              return function () { b.remove(); };
+            })(bit)
+          )
+      );
+    }
+    return Promise.all(done);
+  }
+
   // count rolls a number to a new value instead of swapping it. A chip count that
   // jumps is a variable; one that climbs is a payout.
   function count(el, to, opts) {
@@ -359,6 +418,7 @@
     flyMany: flyMany,
     spot: spot,
     burst: burst,
+    moneyRain: moneyRain,
     count: count,
     centre: centre,
   };