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/elemental-regen.ts

@@ -19,7 +19,7 @@ function makeBaseRegen(id: string, name: string, manaType: string, cost: number)
     manaType: manaType as DisciplineDefinition['manaType'],
     baseCost: cost,
     description: `Attune your ${name.toLowerCase()} mana to regenerate passively over time.`,
-    statBonus: { stat: `regen_${shortId}` as DisciplineDefinition['statBonus']['stat'], baseValue: BASE_REGEN },
+    statBonus: { stat: `regen_${shortId}` as DisciplineDefinition['statBonus']['stat'], baseValue: BASE_REGEN, label: `${name} Regen/tick` },
     difficultyFactor: BASE_DIFF,
     scalingFactor: BASE_SCALE,
     drainBase: BASE_DRAIN,
@@ -61,7 +61,7 @@ export const elementalRegenDisciplines: DisciplineDefinition[] = [
     manaType: 'transference',
     baseCost: 6,
     description: 'Attune your transference mana to regenerate passively over time.',
-    statBonus: { stat: 'regen_transference', baseValue: 0.4 },
+    statBonus: { stat: 'regen_transference', baseValue: 0.4, label: 'Transference Regen/tick' },
     difficultyFactor: 100,
     scalingFactor: 50,
     drainBase: 1,