Performance Optimization for 4-Player Mode

## Problem
STATUS.md identifies performance concerns that need profiling and optimization.

## Areas for Optimization

### 1. 4-Player Collision Detection
- Current: Collision checks spread across 3 frames
- Need: Profile actual performance impact
- Optimize: Algorithm efficiency and frame budget usage

### 2. Frame Budget Usage
- Current: Complex frame budgeting system implemented
- Need: Measure actual CPU cycle usage
- Optimize: Ensure consistent 60 FPS (NTSC) / 50 FPS (PAL)

### 3. Bank Switching Performance
- Current: 64KB bank-switched ROM with 16 banks
- Need: Profile bank switching overhead
- Optimize: Minimize unnecessary bank switches

## Performance Targets
- Maintain 60 FPS in 4-player mode (NTSC)
- Maintain 50 FPS in 4-player mode (PAL)
- Stay within overscan period (~1950 CPU cycles NTSC, ~1630 PAL)

## Implementation Plan
1. Add performance measurement tools
2. Profile current performance in 4-player scenarios
3. Identify bottlenecks
4. Optimize critical paths
5. Verify performance improvements

## Priority
Medium - Important for smooth 4-player gameplay experience

## Estimated Time
4-8 hours for profiling and optimization