refactor: resolve structural inconsistencies and dead code

- Fix broken barrel exports in components/game/index.ts
- Remove skill system from stores (gameStore, gameActions, gameLoopActions, gameHooks, craftingStore, combat)
- Remove skill system from components (page.tsx, LeftPanel, StatsTab, SpellsTab, EnchantmentDesigner, EnchantmentPreparer, GameContext/Provider)
- Delete dead code: stats/ directory, attunements/ directory, layout/ Header+TabBar, shared/ StudyProgress+UpgradeDialog duplicates, effects.ts.fix, study-slice.ts, navigation-slice.ts
- Delete legacy store/ and store-modules/ directories, redirect remaining callers
- Merge root formatting.ts into utils/formatting.ts
- Move effects files (dynamic-compute, upgrade-effects, special-effects, upgrade-effects.types) into effects/ directory
- Move debug-context.tsx into components/game/debug/
- Create tabs/index.ts barrel for tab components
- Fix page.tsx lazy imports to use tabs barrel
- Fix all broken import paths across codebase
- Remove SKILLS_DEF and skill-evolution references
- Trim store.ts to under 400 lines by removing dead skill actions

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

@@ -1,7 +1,7 @@
 // ─── Mana & Regen Utilities ──────────────────────────────────────────────────
 
 import type { GameState } from '../types';
-import type { ComputedEffects } from '../upgrade-effects.types';
+import type { ComputedEffects } from '../effects/upgrade-effects.types';
 import { HOURS_PER_TICK } from '../constants';
 import { getTotalAttunementRegen, getTotalAttunementConversionDrain } from '../data/attunements';
 

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

@@ -0,0 +1,67 @@
+// ─── Pact Utility Functions ───────────────────────────────────────────────────
+
+import { GUARDIANS } from '../constants';
+
+export function computePactMultiplier(state: {
+  signedPacts: number[];
+  pactInterferenceMitigation?: number;
+}): number {
+  const { signedPacts, pactInterferenceMitigation = 0 } = state;
+
+  if (signedPacts.length === 0) return 1.0;
+
+  let baseMult = 1.0;
+  for (const floor of signedPacts) {
+    const guardian = GUARDIANS[floor];
+    if (guardian) {
+      baseMult *= guardian.damageMultiplier;
+    }
+  }
+
+  if (signedPacts.length === 1) return baseMult;
+
+  const numAdditionalPacts = signedPacts.length - 1;
+  const basePenalty = 0.5 * numAdditionalPacts;
+  const mitigationReduction = Math.min(pactInterferenceMitigation, 5) * 0.1;
+  const effectivePenalty = Math.max(0, basePenalty - mitigationReduction);
+
+  if (pactInterferenceMitigation >= 5) {
+    const synergyBonus = (pactInterferenceMitigation - 5) * 0.1;
+    return baseMult * (1 + synergyBonus);
+  }
+
+  return baseMult * (1 - effectivePenalty);
+}
+
+export function computePactInsightMultiplier(state: {
+  signedPacts: number[];
+  pactInterferenceMitigation?: number;
+}): number {
+  const { signedPacts, pactInterferenceMitigation = 0 } = state;
+
+  if (signedPacts.length === 0) return 1.0;
+
+  let mult = 1.0;
+  for (const floor of signedPacts) {
+    const guardian = GUARDIANS[floor];
+    if (guardian) {
+      mult *= guardian.insightMultiplier;
+    }
+  }
+
+  if (signedPacts.length > 1) {
+    const numAdditionalPacts = signedPacts.length - 1;
+    const basePenalty = 0.5 * numAdditionalPacts;
+    const mitigationReduction = Math.min(pactInterferenceMitigation, 5) * 0.1;
+    const effectivePenalty = Math.max(0, basePenalty - mitigationReduction);
+
+    if (pactInterferenceMitigation >= 5) {
+      const synergyBonus = (pactInterferenceMitigation - 5) * 0.1;
+      return mult * (1 + synergyBonus);
+    }
+
+    return mult * (1 - effectivePenalty);
+  }
+
+  return mult;
+}