Fix several UI issues + move colorDead to particle instead of system

[deltakosh]

No description provided.

[bjsplat]

Please make sure to label your PR with "bug", "new feature" or "breaking change" label(s).
To prevent this PR from going to the changelog marked it with the "skip changelog" label.

[bjsplat]

Snapshot stored with reference name:
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Test environment:
https://snapshots-cvgtc2eugrd3cgfd.z01.azurefd.net/refs/pull/17063/merge/index.html

To test a playground add it to the URL, for example:

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https://playground.babylonjs.com/?snapshot=refs/pull/17063/merge
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[bjsplat]

Visualization tests for WebGPU

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[bjsplat]

WebGL2 visualization test reporter:

https://snapshots-cvgtc2eugrd3cgfd.z01.azurefd.net/refs/pull/17063/merge/testResults/webgl2playwright/index.html

[sebavan]

let s mark internal ? or adds the comment ?