cleanup: delete computed-stats.ts shim and store/index.ts

- Delete src/lib/game/computed-stats.ts (root-level re-export shim)
- Delete src/lib/game/store/index.ts (nothing imports from it)
- Update __tests__/computed-stats.test.ts to import from ../utils instead
- Clean up craftingStore.ts imports (remove unused useGameStore, CraftingApply)

Typecheck and lint pass (pre-existing DisciplinesTab.tsx errors unchanged)

src/lib/game/utils/formatting.ts

@@ -1,5 +1,8 @@
 // ─── Formatting Functions ─────────────────────────────────────────────────────
 
+import { ELEMENTS } from '@/lib/game/constants';
+import type { SpellCost } from '@/lib/game/types';
+
 export function fmt(n: number): string {
   if (!isFinite(n) || isNaN(n)) return '0';
   if (n >= 1e9) return (n / 1e9).toFixed(2) + 'B';
@@ -11,3 +14,41 @@ export function fmt(n: number): string {
 export function fmtDec(n: number, d: number = 1): string {
   return isFinite(n) ? n.toFixed(d) : '0';
 }
+
+/**
+ * Format a spell cost for display
+ */
+export function formatSpellCost(cost: SpellCost): string {
+  if (cost.type === 'raw') {
+    return `${cost.amount} raw`;
+  }
+  const elemDef = ELEMENTS[cost.element || ''];
+  return `${cost.amount} ${elemDef?.sym || '?'}`;
+}
+
+/**
+ * Get the display color for a spell cost
+ */
+export function getSpellCostColor(cost: SpellCost): string {
+  if (cost.type === 'raw') {
+    return '#60A5FA'; // Blue for raw mana
+  }
+  return ELEMENTS[cost.element || '']?.color || '#9CA3AF';
+}
+
+/**
+ * Format study time in hours to human-readable string
+ */
+export function formatStudyTime(hours: number): string {
+  if (hours < 1) return `${Math.round(hours * 60)}m`;
+  return `${hours.toFixed(1)}h`;
+}
+
+/**
+ * Format time (hour of day) to HH:MM format
+ */
+export function formatHour(hour: number): string {
+  const h = Math.floor(hour);
+  const m = Math.floor((hour % 1) * 60);
+  return `${h.toString().padStart(2, '0')}:${m.toString().padStart(2, '0')}`;
+}

src/lib/game/utils/index.ts

@@ -1,7 +1,7 @@
 // ─── Game Utilities - Barrel Export ──────────────────────────────────────────
 
 // Re-export everything from the focused modules
-export { fmt, fmtDec } from './formatting';
+export { fmt, fmtDec, formatSpellCost, getSpellCostColor, formatStudyTime, formatHour } from './formatting';
 export { getFloorMaxHP, getFloorElement } from './floor-utils';
 export { 
   computeMaxMana,