Add optional build_zarr_multiscales step to RasterFlow notebooks

[pdarringer]

What

Adds an optional, commented-out-by-default step to each RasterFlow solution notebook that produces a raster (Zarr) output, demonstrating how to build an optimized multiscale Zarr for interactive visualization on cloud.wherobots.com/map.

Each notebook gets two new cells inserted right after the cell that produces the output Zarr:

1. A short markdown description of what build_zarr_multiscales does (adds downsampled overview pyramids so the map can stream coarse tiles when zoomed out and full-resolution pixels when zoomed in).
2. A commented-out code cell calling client.build_zarr_multiscales(source_store=...).

The code is commented out so the notebooks run end-to-end unchanged; users opt in by uncommenting.

Notebooks updated (7)

• RasterFlow_ChangeDetection.ipynb
• RasterFlow_Chesapeake.ipynb
• RasterFlow_FTW.ipynb
• RasterFlow_CHM.ipynb
• RasterFlow_Tile2Net.ipynb
• RasterFlow_Bring_Your_Own_Rasters_NAIP.ipynb (uses client / mosaic_store)
• RasterFlow_S2_Mosaic.ipynb (uses mosaic_store; markdown notes the same call works on all_bands_store)

The correct client variable (rf_client vs client) and source-store variable (model_output_store vs mosaic_store) is used per notebook.

SAM3 notebooks are excluded since they produce vector (GeoParquet) outputs, not rasters.

[gitnotebooks]

Found 7 changed notebooks. Review the changes at https://app.gitnotebooks.com/wherobots/wherobots-examples/pull/162

[notion-workspace]

Add optional build_multiscales step