Fixes #2153

Fixes #2359

Background

TODO

• finish loader implementation and register in base-plugins list
• update the code at

  vitessce/packages/view-types/neuroglancer/src/data-hook-ng-utils.js

  Line 151 in 5bcf8d7

  return useExtractOptionsForNg(loaders, dataset, DataType.OBS_SEGMENTATIONS, matchOn);

  that constructs the initial NG viewerState
  • refactor to use the existing useObsSegmentationsData and useObsPointsData hooks instead. Obtain the URLs returned by these functions, then pass these URLs down to extractDataTypeEntities rather than the manual loader traversal logic

Current demo, with above features: https://legacy.vitessce.io/demos/2026-03-06/405724179/?dataset=neuroglancer-merfish

• Force the user to specify the name of the featureKey and pointIndex columns as part of the fileType options. (We could get it from the spatialdata_attrs or the parquet schema, but this would require an associated spatialdata.zarr store+points element, which introduces complications of keeping the URLs associated to each other, etc.
• Resetting the coordinate system upon color / other state changes.
• Update the selection logic based on the segmentation layer/channel hierarchy
• Obtain the list of segments from the obsFeatureMatrix.obsIndex when obsSets or an obsSetSelection is absent?
  • Related - ensure that the points AND meshes both render in the merfish config example. I think the issue is that the meshes in this dataset are sharded, but we are using a version of NG that does not support this.
• Linting and other cleanup.
• Unit tests for shader generation code

Checklist

• Have tested PR with one or more demo configurations
• Documentation added, updated, or not applicable