Previously, WebgpuTexture.destroy() was an empty method, relying on JavaScript garbage collection to eventually release the underlying GPUTexture. This could cause GPU memory pressure when many textures are destroyed without GC running.

This change updates destroy() to:

• Call gpuTexture.destroy() to immediately release GPU memory
• Clear the texture view and view cache
• Clear cached samplers

This aligns WebGPU behavior with the WebGL implementation, which already calls gl.deleteTexture() on destroy.