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

docs/circular-deps.txt

@@ -1,8 +1,8 @@
 # Circular Dependencies
-Generated: 2026-05-18T09:26:29.031Z
+Generated: 2026-05-18T10:08:43.704Z
 Found: 7 circular chain(s) — these MUST be fixed before modifying involved files.
 
-1. Processed 151 files (1.5s) (37 warnings)
+1. Processed 142 files (1.3s) (37 warnings)
 2. 1) data/equipment/index.ts > data/equipment/utils.ts
 3. 2) data/golems/index.ts > data/golems/utils.ts
 4. 3) stores/combat-actions.ts > stores/combatStore.ts