feat(mesh-layers): Port ScenegraphLayer to WebGPU

[ibgreen]

For #9504

Summary

Port ScenegraphLayer to WebGPU and expose the website demo through the device tabs while keeping the existing WebGL shader paths and behavior intact.

WebGPU verification: ScenegraphLayer renders the bundled 20-plane flight snapshot with the WebGPU tab selected. After load, the console remains free of Scenegraph/WebGPU errors; the expected OpenSky CORS fallback and existing arc source-map warnings remain.

Changes

• Adds a WGSL ScenegraphLayer shader path, including automatic shader-module bindings, instance-index picking, layer opacity, and WebGPU-only depth parameters.
• Adds a Scenegraph-specific WebGPU PBR adapter so glTF base-color textures and the PBR module bindings work with deck.gl's project module.
• Keeps the existing GLSL flat/PBR selection for WebGL; WebGPU-only branches are gated on device.type === 'webgpu'.
• Exposes device to the image-based-lighting callback and marks the legacy gl callback field deprecated in favor of device.handle.
• Enables device tabs for the Scenegraph website demo and updates the WebGPU support docs.
• Makes the flight demo resilient to OpenSky CORS failures: it renders a bundled 20-plane snapshot immediately, then tries the live endpoint updated in update opensky network urls #10465 and falls back cleanly if that request is blocked.

Website examples

Example	WebGL2	WebGPU	Notes
ScenegraphLayer	✅	✅	Renders the bundled flight snapshot; live OpenSky data is best-effort because the API currently blocks cross-origin browser requests.

Validation

• yarn build
• yarn lint (passes with existing repository warnings only)
• Targeted ESLint and Prettier checks for the Scenegraph shader and demo app
• Manual Chrome verification on the website: WebGPU renders 20 airplanes and remains free of Scenegraph/WebGPU console errors after load. Screenshot: feat(mesh-layers): Port ScenegraphLayer to WebGPU #10112 (comment)

[coveralls]

coverage: 83.367% (-0.005%) from 83.372% — ib/webgpu-scenegraph-layer into master

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

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Reviewed commit: 23f2a37ab0

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[chatgpt-codex-connector]

Preserve the IBL dependency for PBR environments

When _lighting: 'pbr' is used together with _imageBasedLightingEnvironment on WebGPU, the glTF parser sets USE_IBL and supplies the environment sampler bindings, and the wrapped stock PBR WGSL still references pbr_diffuseEnvSampler, pbr_specularEnvSampler, and pbr_brdfLUT under that define. Replacing the module dependencies with only lighting drops the ibl module that declares those bindings, so those scenegraphs fail WGSL validation as soon as IBL is enabled; keep the ibl dependency while omitting only the pbrProjection dependency that this wrapper replaces.

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[ibgreen-openai]

Review follow-up: all reviewer threads are addressed and resolved in 23f2a37. Local build, lint, and the focused ScenegraphLayer test passed; GitHub CI is green. This PR is still draft and still requires review before merge.

[ibgreen-openai]

Superseded by the split PRs: #10476 contains only the Scenegraph example local-data/fallback update, and #10477 is the stacked ScenegraphLayer WebGPU port. Closing this combined PR so each change can be reviewed independently.