Fix combined ladder movement in BelowTheSurface

[SEBINSHASAMEERSHA]

Summary

• allow horizontal and vertical ladder input to be processed independently
• fix diagonal ladder movement where horizontal input previously prevented vertical movement
• simplify climb movement state handling

Cause

The ClimbState input logic used a single if/else-if chain for left, right, up, and down movement. This meant horizontal input took priority and prevented vertical movement from being processed when both were held.

Testing

• reviewed the updated input logic and confirmed horizontal and vertical axes are now handled independently
• git diff --check completed successfully
• full runtime testing is currently blocked by pre-existing BelowTheSurface build errors involving center_point(sprite) with the current SplashKit SDK