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/components/game/debug/index.tsx

@@ -1,5 +1,4 @@
 export { GameStateDebug } from './GameStateDebug';
-export { SkillDebug } from './SkillDebug';
 export { ElementDebug } from './ElementDebug';
 export { AttunementDebug } from './AttunementDebug';
 export { GolemDebug } from './GolemDebug';