feat: overhaul mana conversion system to unified regen-deduction model

- New files: element-distance.ts, conversion-costs.ts, conversion-rates.ts
- All conversion types (discipline, attunement, pact) use unified formula
- Conversion costs scale exponentially by element tier (10^(d+1) raw, 10*(d+1) per component)
- Costs deducted from regen, not from mana pool
- Auto-pause on insufficient regen with UI warning
- Meditation boosts conversion rates (reduced by distance)
- Attunement levels provide +50% multiplicative bonus per level
- Guardian pacts provide +0.15/hr base rate + invoker level bonus
- Removed convertMana, processConvertAction, craftComposite from manaStore
- Stats tab shows per-element conversion breakdown with formulas
- ManaDisplay shows per-element net regen rates
- All 916 tests pass, all files under 400 lines

src/lib/game/utils/mana-utils.ts

@@ -3,7 +3,7 @@
 import type { AttunementState } from '../types';
 import type { ComputedEffects } from '../effects/upgrade-effects.types';
 import { HOURS_PER_TICK } from '../constants';
-import { getTotalAttunementRegen, getTotalAttunementConversionDrain } from '../data/attunements';
+import { getTotalAttunementRegen } from '../data/attunements';
 
 export interface DisciplineBonuses {
   bonuses: Record<string, number>;
@@ -84,10 +84,7 @@ export function computeEffectiveRegenForDisplay(
   discipline?: DisciplineBonuses,
 ): { rawRegen: number; conversionDrain: number; effectiveRegen: number } {
   const rawRegen = computeRegen(state, effects, discipline);
-  const conversionDrain = getTotalAttunementConversionDrain(state.attunements || {});
-  const effectiveRegen = Math.max(0, rawRegen - conversionDrain);
-
-  return { rawRegen, conversionDrain, effectiveRegen };
+  return { rawRegen, conversionDrain: 0, effectiveRegen: rawRegen };
 }
 
 // ─── Effective Regen (dynamic) ────────────────────────────────────────────────