fix: show dice in spell cast card, dedupe Alchemy folders, assign signature spells

- Spell cast card now embeds the TS dice (base + overcast) and damage dice
  instead of posting separate roll messages; Dice So Nice still animates.
- Spell pack Alchemy sub-folders renamed to Transmutacja / Warzenie Eliksirów
  so the label no longer repeats under the Alchemia folder.
- Discipline schema gains signatureSpells (the sheet already bound to it);
  build-packs fills it with each discipline's own spells.

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

lang/compendium/en/spells-academic.json

@@ -162,8 +162,8 @@
     "Magia Ognia": {
       "name": "Fire Magic"
     },
-    "Alchemia - Transmutacja": {
-      "name": "Alchemy - Transmutation"
+    "Transmutacja": {
+      "name": "Transmutation"
     },
     "Magia Żywiołów": {
       "name": "Elemental Magic"