Set up template base on DEM vs AOI

Change the set up to build the template from the DEM supplied vs base aoi. Ideally this is based on Lidar extend AOI.

Start by locating the setup entry point and the code that currently builds the template from the base AOI. Read how the supplied DEM and Lidar extent AOI are represented and used; done means the template is built from the intended DEM-derived extent, with the expected preparation workflow still completing successfully.

Written by the indexing model from the issue text.