docs: update refactoring progress - useMagnifierZoom complete

Update progress document to reflect completion of useMagnifierZoom hook:
- Mark useMagnifierZoom as completed in Phase 2
- Add hook details and impact (~150 lines replaced)
- Update remaining work list
- Add commit history entry

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Co-Authored-By: Claude <noreply@anthropic.com>

apps/web/src/arcade-games/know-your-world/.refactoring-progress.md

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+# Magnifier Zoom Refactoring Progress
+
+## Overview
+The MapRenderer.tsx component had grown to 2409 lines with significant code duplication and complex zoom logic. This refactoring aims to improve maintainability by extracting utilities and hooks.
+
+## Completed Work
+
+### Phase 1: Extract Pure Functions ✅
+
+**Created utility modules:**
+
+1. **`utils/screenPixelRatio.ts`**
+   - `calculateScreenPixelRatio()` - Calculate screen pixel ratio from zoom context
+   - `isAboveThreshold()` - Check if ratio exceeds threshold
+   - `calculateMaxZoomAtThreshold()` - Calculate max zoom for capping
+   - `createZoomContext()` - Helper to build context from DOM elements
+   - **Impact**: Replaced 8 duplicated calculations across MapRenderer
+
+2. **`utils/zoomCapping.ts`**
+   - `capZoomAtThreshold()` - Cap zoom with metadata
+   - `wouldZoomBeCapped()` - Simple capping check
+   - **Impact**: Centralizes zoom capping logic with clear API
+
+**Benefits achieved:**
+- ✅ Eliminated significant code duplication
+- ✅ Added comprehensive documentation
+- ✅ Created testable pure functions
+- ✅ All TypeScript passes with no new errors
+
+### Phase 2: Extract Custom Hooks (In Progress)
+
+**Created hooks:**
+
+1. **`hooks/usePointerLock.ts`** ✅
+   - Manages pointer lock state and events
+   - Provides requestPointerLock() and exitPointerLock() methods
+   - Includes onLockAcquired/onLockReleased callbacks
+   - Automatic cleanup on unmount
+
+2. **`hooks/useMagnifierZoom.ts`** ✅
+   - Manages zoom state (targetZoom, uncappedAdaptiveZoomRef)
+   - React Spring animation with configurable easing
+   - Automatic pause/resume at precision mode threshold
+   - Zoom capping when pointer lock state changes
+   - Recalculation of capped zoom on pointer lock release
+   - **Impact**: Replaces ~150 lines of zoom-related logic in MapRenderer
+
+**Still TODO:**
+- `hooks/useRegionDetection.ts` - Region detection for zoom calculation
+
+## Remaining Work
+
+### Phase 1 (Optional)
+- Extract adaptive zoom search algorithm to `utils/adaptiveZoomSearch.ts`
+  - **Note**: This is complex (~200 lines) and can be done separately
+
+### Phase 2 (Partial)
+- Create `useRegionDetection` hook
+- Create `useMagnifierPosition` hook (optional)
+
+### Phase 3
+- Simplify MapRenderer to compose hooks
+- Reduce MapRenderer.tsx from 2409 lines to ~300-500 lines
+
+### Phase 4
+- Create `MAGNIFIER_ARCHITECTURE.md` documentation
+- Document the zoom algorithm and system architecture
+- Add JSDoc comments to remaining exported functions
+
+## Key Learnings
+
+1. **Screen Pixel Ratio** is the core metric (how many screen pixels the magnifier "jumps" per mouse pixel)
+2. **Precision Mode Threshold** (20 px/px) determines when to recommend pointer lock
+3. **Zoom Capping** prevents excessive sensitivity before precision mode activates
+4. **Adaptive Zoom Search** finds optimal zoom based on detected region sizes
+
+## Testing Strategy
+
+- No behavior changes - purely structural refactors
+- TypeScript catches interface issues
+- Manual testing on dev server
+- All code remains backward compatible
+
+## Files Modified
+
+### New Files Created
+- `utils/screenPixelRatio.ts` (130 lines)
+- `utils/zoomCapping.ts` (122 lines)
+- `hooks/usePointerLock.ts` (119 lines)
+- `hooks/useMagnifierZoom.ts` (240 lines)
+
+### Modified Files
+- `components/MapRenderer.tsx` (replaced 8 calculations with utility calls)
+
+## Next Steps
+
+When continuing:
+1. Test current changes on dev server
+2. Create remaining hooks (useRegionDetection)
+3. Begin Phase 3 - integrate hooks into MapRenderer
+4. Measure final line count reduction
+5. Create architecture documentation
+
+## Commit History
+
+1. `efb39b01` - Phase 1: Extract screenPixelRatio.ts, replace 5 instances
+2. `360f8409` - Phase 1: Complete screenPixelRatio refactoring, replace remaining 3 instances
+3. `44d99bc4` - Phase 1: Extract zoomCapping.ts utility
+4. `d5b16d5f` - Phase 2: Extract usePointerLock hook
+5. `ef86f00f` - Phase 2: Extract useMagnifierZoom hook