refactor: Replace natural-regen disciplines with mana conversion speed disciplines

- Add conversionRate + sourceManaTypes fields to DisciplineDefinition
- Rewrite elemental-regen.ts: 8 base disciplines now convert raw→element
- Rewrite elemental-regen-advanced.ts: 6 composite/exotic disciplines with proper source recipes
- Update discipline-effects.ts: produce conversion entries instead of regen bonuses
- Update gameStore.ts tick: drain source mana types, add to target element
- Update discipline-slice.ts: gate activation on source mana type access
- Update discipline-math.ts: resolve mana type IDs to 'X mana' display names
- Update DisciplinesTab.tsx: show conversion info, source requirements, and lock state
- Update DisciplineDebugSection.tsx: pass elements to activate()
- Update effects.ts: remove regen_{element} merge (no longer produced)

src/lib/game/utils/discipline-math.ts

@@ -87,10 +87,31 @@ export function canProceedDiscipline(
   return element && element.current >= drain;
 }
 
+// ─── Known mana type names for display ────────────────────────────────────────
+const MANA_TYPE_NAMES: Record<string, string> = {
+  raw: 'raw',
+  fire: 'fire',
+  water: 'water',
+  air: 'air',
+  earth: 'earth',
+  light: 'light',
+  dark: 'dark',
+  death: 'death',
+  transference: 'transference',
+  metal: 'metal',
+  sand: 'sand',
+  lightning: 'lightning',
+  crystal: 'crystal',
+  stellar: 'stellar',
+  void: 'void',
+};
+
 /**
  * Check if a discipline's prerequisites are met.
+ * For disciplines with sourceManaTypes (conversion disciplines), requires are
+ * mana type IDs that must be unlocked (e.g. fire, earth).
  * Returns { canProceed: boolean, missingPrereqs: string[] }
- * where missingPrereqs is a list of prerequisite discipline names that are not yet unlocked.
+ * where missingPrereqs is a list of human-readable prerequisite descriptions.
  */
 export function checkDisciplinePrerequisites(
   discipline: DisciplineDefinition,
@@ -104,11 +125,21 @@ export function checkDisciplinePrerequisites(
   const missingPrereqs: string[] = [];
 
   for (const reqId of discipline.requires) {
-    const reqState = allDisciplines[reqId];
-    // A prerequisite is met if the discipline has XP > 0 (has been practiced)
-    if (!reqState || reqState.xp <= 0) {
-      const reqDef = allDefinitions.find((d) => d.id === reqId);
-      missingPrereqs.push(reqDef?.name ?? reqId);
+    // Check if this is a discipline prerequisite (exists in definitions)
+    const reqDef = allDefinitions.find((d) => d.id === reqId);
+    if (reqDef) {
+      const reqState = allDisciplines[reqId];
+      if (!reqState || reqState.xp <= 0) {
+        missingPrereqs.push(reqDef?.name ?? reqId);
+      }
+    } else {
+      // Treat as mana type requirement — display as "<name> mana"
+      const typeName = MANA_TYPE_NAMES[reqId];
+      if (typeName) {
+        missingPrereqs.push(`${typeName} mana`);
+      } else {
+        missingPrereqs.push(reqId);
+      }
     }
   }