Elimina el kernel Metal O(N²) de boids en GPU que causava GPU timeout
a macOS amb >50K boles, arrossegant WindowServer fins al crash.
- Elimina gpu_boid_buffer.hpp/cpp (GpuBoidBuffer, BallComputeData, BoidParams)
- Elimina kBoidComputeMSL i kBallComputeVertMSL de gpu_pipeline
- Elimina boid_compute_pipeline_ i ball_compute_pipeline_
- Elimina use_gpu_boids_, boid_params_, ball_screen_uniforms_ de Engine
- Elimina syncAndExitGpuBoids() i tot el compute dispatch de render()
- Mode BOIDS ara usa sempre boid_manager_ (CPU, spatial hash O(N))
i renderitza via gpu_ball_buffer_ instanced (mateix path que PHYSICS)
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
