550x350 m clipped to the block, already in the project CRS, 984 KB, committed
through LFS. Verified against the service's own point query and the earlier
probe: 115.911/119.422/117.593 m, agreement within 6 cm.
Adds Geo/scripts/dem_stats.py, a stdlib tiled-TIFF reader, because GDAL cannot
run on the host and the exported raster is tiled rather than strip-organised.
Probe 22 points with the USGS 3DEP point service: walkable surfaces span
115.65-119.59 m, a 3.94 m relief, so elevation data is required by the AGENTS
rule. Grade falls ~3.3 m eastward over the 279 m block (1.2%) and the north
sidewalk sits 0.4-0.7 m above the south. 3DEP 1 m is public domain and becomes
the chosen source; the tile itself is still to be downloaded.
Factored the shared OSM helpers into Geo/scripts/osm_common.py so the street
profile and the elevation probe read the same geometry.
zwitschi