Gaussian splats not pickable

[MAG-AdrianMeredith]

In gsplat-compressed-material.js there is the following code:

        #ifdef PICK_PASS
            if (B < 0.3) {
                discard;
            }
            return uColor;
        #endif

Where its expecting the colour picker color as uColor however this is no longer how the picker works and instead the color is derived from the mesh_instance_id parameter from

getPickOutput()

Steps to Reproduce

1. add a gaussian splat
2. attempt to pick it
3. the pick colour is rendered black and no selection picked

[MAG-AdrianMeredith]

Interesting theres no equivalent in gsplat-material.js.

[mvaligursky]

yep definitely something we need to fix.