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/stores/discipline-slice.ts

@@ -89,9 +89,23 @@ export const useDisciplineStore = create<DisciplineStore>()(
           }).length;
           if (nonPaused >= s.concurrentLimit) return s;
           if (!canProceedDiscipline(def, existing, gameState)) return s;
+
+          // Check discipline prerequisites (requires field → discipline XP)
           const prereqCheck = checkDisciplinePrerequisites(def, s.disciplines, ALL_DISCIPLINES);
           if (!prereqCheck.canProceed) return s;
 
+          // For conversion disciplines: gate on having all source mana types unlocked
+          if (def.sourceManaTypes && def.sourceManaTypes.length > 0) {
+            const elements = gameState?.elements;
+            if (elements) {
+              for (const srcType of def.sourceManaTypes) {
+                if (srcType === 'raw') continue; // raw is always available
+                const srcElem = elements[srcType];
+                if (!srcElem || !srcElem.unlocked) return s;
+              }
+            }
+          }
+
           const discState = existing || { id, xp: 0, paused: false };
           // Set currentAction to 'practicing' (only overrides 'meditate')
           useCombatStore.getState().startPracticing();