refactor: Major codebase refactoring for maintainability

Store refactoring (2138 → 1651 lines, 23% reduction):
- Extract computed-stats.ts with 18 utility functions
- Extract navigation-slice.ts for floor navigation actions
- Extract study-slice.ts for study-related actions
- Move fmt/fmtDec to computed-stats, re-export from formatting

Page refactoring (2554 → 1695 lines, 34% reduction):
- Use existing SpireTab component instead of inline render
- Extract ActionButtons component
- Extract CalendarDisplay component
- Extract CraftingProgress component
- Extract StudyProgress component
- Extract ManaDisplay component
- Extract TimeDisplay component
- Create tabs/index.ts for cleaner exports

This improves code organization and makes the codebase more maintainable.

worklog.md

@@ -309,3 +309,134 @@ Stage Summary:
 - Multi-casting is fully functional
 - Game compiles and runs without errors
 - Lint passes with no issues
+
+---
+## Task ID: 3 - Component Refactoring
+### Work Task
+Refactor `/home/z/my-project/src/app/page.tsx` to use existing tab components and extract new components. The file was ~2500 lines with inline render functions duplicating existing tab components.
+
+### Work Summary
+**Components Created:**
+1. `ActionButtons.tsx` - Extracted from `renderActionButtons()`, handles main action buttons (Meditate, Climb, Study, Convert) and crafting action buttons
+2. `CalendarDisplay.tsx` - Extracted from `renderCalendar()`, renders the day calendar with incursion indicators
+3. `CraftingProgress.tsx` - Extracted from `renderCraftingProgress()`, shows design/preparation/application progress bars
+4. `StudyProgress.tsx` - Extracted from `renderStudyProgress()`, displays current study progress with cancel button
+5. `ManaDisplay.tsx` - New component for mana/gathering section with progress bar and gather button
+6. `TimeDisplay.tsx` - New component for day/hour display with pause toggle
+
+**Tab Components Updated:**
+- `SpireTab.tsx` - Updated to include all functionality from inline version:
+  - Multi-spell support with activeEquipmentSpells
+  - Individual cast progress bars for each spell
+  - DPS calculation for multiple spells
+  - Parallel study support
+  - Crafting progress display
+  - ComboMeter integration
+  - Known Spells display
+  - Activity Log
+
+**File Changes:**
+- `page.tsx` reduced from ~2555 lines to 1695 lines (34% reduction)
+- Removed inline render functions: `renderCalendar`, `renderActionButtons`, `renderCraftingProgress`, `renderStudyProgress`, `renderSpireTab`, `renderSpellsTab`, `renderLabTab`
+- Updated imports to use extracted components
+- Cleaned up unused imports (`MAX_DAY`, `INCURSION_START_DAY`, `MANA_PER_ELEMENT`)
+- Created `tabs/index.ts` for cleaner tab component exports
+- Updated `game/index.ts` to export all new components
+
+**Results:**
+- All lint checks pass
+- Functionality preserved - all features working as before
+- Better code organization with reusable components
+- Easier maintenance with separated concerns
+
+---
+## Task ID: 1 - Code Extraction
+### Work Task
+Extract computed stats and utility functions from `/home/z/my-project/src/lib/game/store.ts` into a new file `/home/z/my-project/src/lib/game/computed-stats.ts`. The store.ts was ~2100 lines with functions that could be better organized in a separate module.
+
+### Work Summary
+**Created New File:** `computed-stats.ts`
+
+**Functions Extracted:**
+1. `DEFAULT_EFFECTS` constant - Default empty effects object for computed effects
+2. `fmt` and `fmtDec` - Number formatting utilities (K, M, B suffixes)
+3. `getFloorMaxHP` - Floor HP calculation with guardian and scaling logic
+4. `getFloorElement` - Floor element determination from cycle
+5. `getActiveEquipmentSpells` - Helper to get all spells from equipped caster weapons
+6. `getEffectiveSkillLevel` - Helper for tiered skill level calculation
+7. `computeMaxMana` - Maximum mana calculation with effects
+8. `computeElementMax` - Elemental mana capacity calculation
+9. `computeRegen` - Mana regeneration rate calculation
+10. `computeEffectiveRegen` - Regen with dynamic special effects
+11. `computeClickMana` - Click mana gain calculation
+12. `getElementalBonus` - Elemental damage bonus helper
+13. `calcDamage` - Damage calculation with skills, pacts, and crits
+14. `calcInsight` - End-of-loop insight calculation
+15. `getMeditationBonus` - Meditation multiplier calculation
+16. `getIncursionStrength` - Time-based incursion penalty
+17. `canAffordSpellCost` - Check if player can afford spell
+18. `deductSpellCost` - Deduct spell cost from mana pool
+
+**Files Updated:**
+- `store.ts`: 
+  - Added imports from computed-stats.ts
+  - Removed duplicate function definitions
+  - Kept local `getElementalBonus` helper (used only in store)
+  - Re-exports `fmt` and `fmtDec` for backward compatibility
+- `formatting.ts`:
+  - Added re-exports of `fmt` and `fmtDec` from computed-stats.ts
+
+**Results:**
+- All lint checks pass
+- No functionality changed - pure refactoring
+- Better code organization with computed stats in dedicated module
+- Easier to test and maintain individual functions
+- Backward compatible - existing imports still work
+
+---
+## Task ID: 2 - Store Slice Refactoring
+### Work Task
+Create two new store slices to reduce the size of `/home/z/my-project/src/lib/game/store.ts`:
+1. `navigation-slice.ts` - Extract navigation-related actions
+2. `study-slice.ts` - Extract study-related actions
+
+### Work Summary
+**Created New Files:**
+
+**1. `navigation-slice.ts`** - Floor navigation actions:
+- `NavigationActions` interface defining the action types
+- `createNavigationSlice()` factory function
+- `setClimbDirection()` - Set climbing direction (up/down)
+- `changeFloor()` - Manually change floors with respawn logic
+
+**2. `study-slice.ts`** - Study system actions:
+- `StudyActions` interface defining the action types
+- `createStudySlice()` factory function
+- `startStudyingSkill()` - Begin studying a skill with prerequisite and cost checks
+- `startStudyingSpell()` - Begin studying a spell with cost checks
+- `cancelStudy()` - Cancel current study with progress retention bonus
+- `startParallelStudySkill()` - Start parallel study (requires Parallel Mind upgrade)
+- `cancelParallelStudy()` - Cancel parallel study
+
+**Files Updated:**
+- `store.ts`:
+  - Added imports for `createNavigationSlice` and `createStudySlice`
+  - Added imports for `NavigationActions` and `StudyActions` interfaces
+  - Updated `GameStore` interface to extend both new action interfaces
+  - Spread the new slices into the store
+  - Removed duplicated action implementations
+  - Added re-exports for computed stats functions (`getFloorElement`, `computeMaxMana`, `computeRegen`, `computeClickMana`, `calcDamage`, `getMeditationBonus`, `getIncursionStrength`, `canAffordSpellCost`, `getFloorMaxHP`)
+  - Added missing imports for `EQUIPMENT_TYPES` and `EquipmentInstance`
+
+**Pattern Followed:**
+- Followed existing slice patterns from `familiar-slice.ts` and `crafting-slice.ts`
+- Used factory function pattern that accepts `set` and `get` from Zustand
+- Exported both the interface and factory function
+- Proper TypeScript typing throughout
+
+**Results:**
+- All lint checks pass
+- No functionality changed - pure refactoring
+- Reduced store.ts size by extracting ~100 lines of action implementations
+- Better code organization with navigation and study logic in dedicated modules
+- Easier to maintain and extend individual features