Thumb of God gets its ceremony: prompt, sighted dimming, and the die

The cast always worked (click a square), but nothing guided it and
nothing marked its arrival. Now: a targeting prompt, eligibility
dimming to the caster's sighted squares (the engine demands LOS to the
aim point), and a flourish — the aiming mark, a shadow gathering, the
die crashing down out of a clear sky with a bounce and flung grit, a
drift line when fate moves it, and every scattered token streaking to
where it lands. In the /?fx gallery as die-drop.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0138A8CjeQRpvzKxuMfz1Bqc

packages/web/src/App.svelte

@@ -271,6 +271,7 @@
     "create-door": "click a wall for the new door",
     "warp-wand": "click a wall to warp it open",
     "stone-to-water": "click a stone wall, or a stone-filled square",
+    "thumb-of-god": "aim the die at a square in sight — it may drift on impact",
     "dispel-creation": "click the creation — a square, a creature, or a conjured wall",
   };
   const EDGE_CARDS = new Set([