feat(effects): Add clustered volumetrics, adaptive HDR exposure, and cinematic bloom

[ibgreen-openai]

Goals

• Add reusable, physically grounded atmospheric light transport and HDR camera response to the composable WebGPU deferred-rendering stack.
• Make individual rendering effects, output quality, and performance tradeoffs discoverable in the example controls.

Changes

• Add clustered volumetric lighting with participating-media integration, exponential height fog, Beer-Lambert extinction, anisotropic phase response, clustered point-light scattering, directional occlusion, temporal history, and bilateral denoising.
• Add configurable depth-occluded crepuscular god rays with dedicated controls and diagnostics.
• Eliminate cluster-shaped fog seams by selecting stable nearby lights across neighboring clusters and handling light-list overflow.
• Add fully GPU-resident HDR auto exposure with center-weighted logarithmic luminance metering, a reduction pyramid, persistent adaptation, and independently adjustable brightening/darkening speeds.
• Add cinematic HDR bloom using configurable floating-point multiscale targets; correct bloom filtering so isolated emissive highlights fade smoothly without square ringing or halo plateaus.
• Preserve named settings sections as accessible effect accordions in Illumination Lab and Visualization City, including independent effect enable switches and HDR camera/bloom sections.
• Default SSAO, GTAO, SSGI, SSR, and clustered volumetrics to full-resolution intermediate framebuffers; expose per-effect buffer-resolution controls.
• Expand shader-pipeline documentation, rendering-technique comparisons, effect guidance, GPU image-regression coverage, and browser/WebGPU shader coverage.

Verification

• corepack yarn build
• corepack yarn lint fix
• corepack yarn test-headless modules/effects/test/passes/image-blur-filters/bloom.spec.ts modules/effects/test/passes/advanced-effects.spec.ts modules/effects/test/passes/postprocessing-wgsl.spec.ts - 7 focused tests passed, including bloom image readback.
• Commit hook node suite - 178 tests passed, 2 skipped.
• corepack yarn workspace luma.gl-examples-experimental-deferred-rendering build
• corepack yarn workspace luma.gl-examples-experimental-advanced-effects build

Notes

• Full resolution is the quality-first default; applications can lower individual effect resolution scales where GPU cost matters.
• The PR remains based directly on master; its global-illumination prerequisite has already merged.