geo: one tool directory, one unit boundary, per-asset provenance

Geo/tools/ is now every geographic script, with Geo/README.md documenting each
one; the Blender-side builders moved beside their outputs in Art/blender/*/ and
import their helpers from Geo/tools/osm_common.py.

That module gains to_unreal_local() and to_blender_local(): the only place in the
repository that multiplies metres by 100, so a second silent scale cannot be
introduced. block_height_report.py adds height provenance for the block — 3 of
15 buildings have no height data and render at a placeholder 6.4 m.
asset_metadata.py writes and audits <asset>.geo.json sidecars; four now exist
(hero-facade, terrain, street, blockout) and the audit recomputes each centre from
the origin, failing anything that disagrees.

Docs/setup.md

@@ -61,7 +61,7 @@ The archive on disk is **Unreal Engine 5.2.0**, released May 2023, three and a h
 - `[x]` Blender 5.2 LTS (Flatpak) and MPFB 2.0.18 recorded.
 - `[x]` Install QGIS and record its version. QGIS **4.2.3**, Flatpak `stable`, runtime `org.kde.Platform 6.11`, bundled PROJ `9.9.0`. The stale `lts` 3.28.9 install was uninstalled 2026-11-07; only `stable` remains.
 - `[x]` Install Blosm in Blender, record its version, and confirm it loads on Blender 5.2. Blosm **2.7.28** imports the block extract headless in `3Dsimple` mode; the exact command and the two required headless workarounds are in `Art/blender/README.md`. No second Blender version was needed.
-- `[ ]` **Optional.** Confirm the geo tool Python environment (venv with `pyproj`, `GDAL`, `shapely`). Not needed so far: every geo script in `Geo/scripts/` is standard-library only, and PROJ 9.9.0 is invoked from the QGIS Flatpak (`LD_LIBRARY_PATH` trick in `Geo/manifests/local-origin.md`). Add the venv only when a step genuinely needs `pyproj` or GDAL in-process.
+- `[ ]` **Optional.** Confirm the geo tool Python environment (venv with `pyproj`, `GDAL`, `shapely`). Not needed so far: every geo script in `Geo/tools/` is standard-library only, and PROJ 9.9.0 is invoked from the QGIS Flatpak (`LD_LIBRARY_PATH` trick in `Geo/manifests/local-origin.md`). Add the venv only when a step genuinely needs `pyproj` or GDAL in-process.
 
 ## 4. Project bootstrap