feat: discipline UI improvements - stat labels, prerequisites, mana type tab

- Add player-friendly label field to statBonus in DisciplineDefinition
- Show prerequisite requirements on locked discipline cards
- Disable activate button for locked disciplines
- Restructure elemental attunement into dedicated 'Mana Types' tab
- Add checkDisciplinePrerequisites utility function
- Update store to enforce prerequisite checking on activation
- Split discipline-prerequisites tests into separate file

src/lib/game/data/disciplines/base.ts

@@ -12,7 +12,7 @@ export const baseDisciplines: DisciplineDefinition[] = [
     manaType: 'raw',
     baseCost: 5,
     description: 'Learn to harness raw mana more efficiently.',
-    statBonus: { stat: 'maxManaBonus', baseValue: 10 },
+    statBonus: { stat: 'maxManaBonus', baseValue: 10, label: 'Max Mana' },
     difficultyFactor: 100,
     scalingFactor: 50,
     drainBase: 1,
@@ -33,25 +33,4 @@ export const baseDisciplines: DisciplineDefinition[] = [
       },
     ],
   },
-  {
-    id: 'elemental-attunement',
-    name: 'Elemental Attunement',
-    attunement: DisciplinesAttunementType.BASE,
-    manaType: 'fire',
-    baseCost: 10,
-    description: 'Begin focusing raw mana into fire.',
-    statBonus: { stat: 'elementCap_fire', baseValue: 5 },
-    difficultyFactor: 150,
-    scalingFactor: 75,
-    drainBase: 2,
-    perks: [
-      {
-        id: 'elem-attunement-1',
-        type: 'once',
-        threshold: 200,
-        value: 0,
-        description: '+10 Fire Capacity',
-      },
-    ],
-  },
 ];