RFC/POC: support float16 postprocess buffers

[ibgreen-openai]

Goal

Allow deck.gl postprocessing effects to preserve HDR highlight energy before effects such as bloom consume the rendered scene.

Changes

• Add postProcessColorFormat to DeckProps, defaulting to the existing rgba8unorm behavior.
• Support explicit rgba16float postprocess ping-pong buffers.
• Recreate intermediate framebuffers when the configured format changes.
• Validate that the requested format is renderable and linearly filterable before allocating buffers.
• Export PostProcessColorFormat for callers configuring HDR effects.
• Add coverage for float16 allocation and switching back to unorm buffers.

Context

This is intentionally an RFC/POC. luma.gl v10 has HDR-capable WebGPU canvas support, but deck.gl currently clips highlights in its rgba8unorm postprocess intermediates before a bloom effect can read them. This change provides the deck.gl-side opt-in without changing the default rendering path.

Example:

new Deck({
  postProcessColorFormat: 'rgba16float',
  effects: [bloomEffect]
});

Validation

• yarn vitest run test/modules/core/lib/deck-renderer.spec.ts
• yarn build
• yarn lint was run; it is blocked only by unrelated existing formatting in modules/core/src/passes/layers-pass.ts.

[coveralls]

coverage: 83.757% (-0.004%) from 83.761% — codex/rfc-poc-hdr-postprocess-buffers into master