- Added useManaStore import to skillStore.ts
- Added mana deduction logic in startStudyingSkill action
- Mana is now properly deducted when starting to study a skill (unless already paid)
- SkillsTab.tsx: Replace useGameStore with useSkillStore for currentStudyTarget
- SkillUpgradeDialog.tsx: Migrate to useSkillStore, fix commitSkillUpgrades call
- SkillRow.tsx: Remove parallel study feature (startParallelStudySkill doesn't exist in skillStore), remove hasParallelStudy reference
- Update index.ts export to point to new SkillsTab location
- Delete old legacy tabs/SkillsTab.tsx file