request: being able to explicitly declare vertex-buffer slots for pipelines

TypeGPU currently assigns vertex-buffer slots consecutively in order in which vertex layouts were encountered by the shader - 0, 1, 2 etc.

I'm working on a project where it's much easier to reason about and handle things if slots were fixed. I wanted to make it so:

• Slot 0: standard vertex data
• Slot 1: skinning data
• Slot 2: vertex colors
• Slots 3+: custom

Not every pipeline has to use every slot. For example, an unskinned pipeline would use standard vertex data and vertex colors (slots 0 and 2). WebGPU supports this via null values like buffers: [standardLayout, null, colorLayout].

In the above case, typeGPU would assign the color layout to slot 1 and I couldnt find any way to reserve the unused slot (without unwrapping everything and just using basically vanilla webgpu).

Could TypeGPU support optional per pipeline slot mapping as an opt-in? I think it's totally possible to make it so current DX is unchanged while adding this as optional

root.createRenderPipeline({
    vertex,
    fragment,
    attribs,
    vertexBufferSlots: [standardLayout, null, colorLayout]
  });

This would make slots allocation predictable across pipeline variants, so render passes would not need to know which optional layouts a particular pipeline consumes.

When vertexBufferSlot option is not present, existing behaviour of assigning slots in order would remain unchanged.

Start at the root.createRenderPipeline entry point and trace how vertex layouts become buffer slots. Compare the proposed vertexBufferSlots array, including null entries, with the existing automatic allocation path. Done means opt-in fixed slots work across pipeline variants while pipelines without the option retain their current behavior.