DJI Terra already emits standard XYZ z/x/y trees, so a good capture does not
need slicing again. scripts/import-tiles.ps1 validates the source, refuses a
tile-extension mismatch, copies it into the scan root, writes the manifest and
triggers a scan.
The extension check is the point: detectTileFormat picks whichever tile it
happens to see first and the published URL template uses that single extension,
so a layer mixing .png and .webp silently 404s half its tiles.
GUIDE.md gains the mixed workflow: import for the captures that are good as-is,
slice the GeoTIFF when the layer needs to be rebuildable as a mosaic.
