feat(geo): adopt Mapbox building calibration (3.1 m per level)

Owner decision: adopt the two findings from the Mapbox cross-check.

- LEVEL_HEIGHT 3.2 -> 3.1 m in block_height_report.py and the Blosm
  --level-height default; every levels-derived building drops ~0.6 m per 6
  levels, matching Mapbox.
- HEIGHT_OVERRIDES for the three rear building=yes/apartments structures that
  Mapbox gives as single storey (3.0 m) where our 2-level fallback rendered
  6.4 m blocks.
- classify_height() takes an optional way_id so overrides apply; the Mapbox
  cross-check passes it and now reports 66 match / 6 non-building / 0 disagree.
- Geometry follows: blockout regenerated at 3.1 (frontage object names
  preserved, 6/6 exported), frontage re-imported, DemoMap rebuilt, packaged
  -qaselftest PASS (walk, reset, pause, transect 0 holes, wall probe 0/35).
- Docs: Art/blender/README scale table + a note that Blosm adds ~1.9 m roof mass
  above levels x levelHeight; TODO item closed; MEMORY records the gotcha that
  blockout regeneration must re-verify the element.* frontage mapping.

Geo/tools/mapbox_buildings.py

@@ -184,7 +184,7 @@ def build_rows(nodes, ways, token, radius, max_distance, delay) -> list[dict]:
         lat, lon = centroid_lat_lon(points)
         payload, cached = tilequery(lat, lon, token, radius, delay)
         feature = nearest_building(payload, max_distance)
-        ours_height, ours_source = bhr.classify_height(tags)
+        ours_height, ours_source = bhr.classify_height(tags, way_id=wid)
         theirs = None if feature is None else feature.get("height")
         verdict, delta = compare(ours_height, ours_source, theirs)
         rows.append({