Client-side visualization of embeddings

Placeholder ticket to track adding visualization tools for embeddings (either pre-generated like AlphaEarth or generated on-the-fly like Tessera/OlmoEarth).

We could go down a few paths depending on the embedding storage format + visualization library:

| Combinations | Storage format uptake | Visualization notes |
|--|--|--|
|GeoParquet + Lonboard |Format proposed at [cloudnativegeo/geo-embeddings-survey](https://github.com/cloudnativegeo/geo-embeddings-survey?tab=readme-ov-file#survey-for-current-practices-storing-embeddings-in-geoparquet), used initially in Clay v0 [see schema](https://clay-foundation.github.io/model/clay-v0/model_embeddings.html#table-schema) and EarthIndex | Lonboard is fairly mature, but does it support visualization based on FixedShapeTensorArray? |
| GeoTIFF/Zarr + [deck.gl-raster](https://github.com/developmentseed/deck.gl-raster) | [GeoTessera](https://github.com/ucam-eo/geotessera/tree/v0.7.3?tab=readme-ov-file#download-embeddings) supports GeoTIFF and [Zarr (since v0.7.1)](https://github.com/ucam-eo/geotessera/releases/tag/v0.7.1); OlmoEarth supports [GeoTIFF export](https://github.com/allenai/rslearn/blob/v0.0.20/docs/examples/OlmoEarthEmbeddings.md#compute-and-save-embeddings); AlphaEarth is in [COG](https://source.coop/tge-labs/aef) | GeoTIFF/COG viz is usable in deck.gl-raster, Zarr would need some work - https://github.com/developmentseed/deck.gl-raster/issues/166 |

To be worked on during DevSeed's annual gathering end of Feb 2026 at a workshop.
- Core goal: Visualize COGs only, just the first three bands in the embedding array for each pixel
- Stretch goal: Visualize Zarr (!), and/or do some dimensionality reduction (e.g. PCA, UMAP, etc) and then render as RGB