Implement deferred destruction for WebGPU textures

[mvaligursky]

This PR fixes GPU resource management for WebGPU textures:

• WebgpuTexture.destroy() was previously empty, relying on JavaScript garbage collection to eventually release the underlying GPUTexture. This could cause GPU memory pressure when many textures are destroyed.

• However, calling gpuTexture.destroy() immediately causes WebGPU validation errors ("Destroyed texture used in a submit") because command buffers referencing the texture may not have been submitted yet.

This PR implements deferred destruction:

• Adds a _deferredDestroys queue to WebgpuGraphicsDevice
• GPU resources are queued for destruction via deferDestroy()
• Resources are destroyed after submit() completes, ensuring all pending commands have been submitted
• Updates WebgpuTexture.destroy() to use deferred destruction

This ensures GPU memory is released promptly while avoiding use-after-destroy validation errors.

[Copilot]

Pull request overview

This PR implements deferred destruction for WebGPU textures to prevent validation errors that occur when GPU resources are destroyed while still referenced by pending command buffers.

Changes:

• Adds a _deferredDestroys queue to WebgpuGraphicsDevice to track GPU resources awaiting destruction
• Implements a deferDestroy() method that queues resources for destruction after command buffer submission
• Updates WebgpuTexture.destroy() to use deferred destruction instead of immediate destruction

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
src/platform/graphics/webgpu/webgpu-graphics-device.js	Adds deferred destruction infrastructure with queue management and processing after command buffer submission
src/platform/graphics/webgpu/webgpu-texture.js	Updates texture destruction to use deferred mechanism instead of immediate GPU resource cleanup

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