fix: attunement system spec-vs-code discrepancies (issue #331)

- Fix conversion rate level scaling from linear (1+level*0.5) to exponential (1.5^(level-1)) in conversion-rates.ts
- Fix getAttunementLevelMultiplier formula to match spec §4.3
- Add level-up logging in attunementStore.ts via combat store addActivityLog
- Clarify getAttunementConversionRate returns flat base rate (level scaling applied separately)
- Update spec §8 to describe time-based puzzle room system matching code implementation
- Add 17 regression tests verifying exponential scaling, base rate behavior, and spec table values

src/lib/game/utils/conversion-rates.ts

@@ -24,7 +24,7 @@ export interface ConversionRateEntry {
   pactBase: number;
   /** Sum of base rates */
   baseRate: number;
-  /** Attunement level multiplier: 1 + Σ(relevantAttunementLevel × 0.5) */
+  /** Attunement level multiplier: 1 + Σ(1.5^(attunementLevel-1) - 1) per relevant attunement */
   attunementMult: number;
   /** Pact level multiplier: 1 + Σ(pactCount_element × invokerLevel × 0.25) */
   pactMult: number;
@@ -100,13 +100,13 @@ export function computeConversionRates(params: ConversionRateParams): Conversion
   let totalRawDrain = 0;
 
   // ── Step 1: Compute attunement level bonuses per element ──────────
-  // Each attunement level adds +0.5 to the multiplier for conversions
+  // Each attunement contributes 1.5^(level-1) exponential scaling to conversions
   // where the attunement's primary element is the destination or a component.
   const attunementBonuses: Record<string, number> = {};
   for (const [id, state] of Object.entries(attunements)) {
     if (!state.active) continue;
     const level = state.level || 1;
-    const bonus = level * 0.5;
+    const bonus = Math.pow(1.5, level - 1) - 1;
 
     // Determine which elements this attunement boosts based on its primary mana type
     for (const [elem, cost] of Object.entries(CONVERSION_COSTS)) {