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.

MEMORY.md

@@ -52,7 +52,7 @@ Scope: facts and traps that cost time to establish. Planned work lives in [ROADM
 
 ## 2026-11-06 — Geo data traps
 
-- **The 3DEP export is a tiled TIFF, not strips.** A strip reader silently scrambles rows and produces fake 0 m / 127 m bands. `Geo/scripts/dem_stats.py` handles tiles.
+- **The 3DEP export is a tiled TIFF, not strips.** A strip reader silently scrambles rows and produces fake 0 m / 127 m bands. `Geo/tools/dem_stats.py` handles tiles.
 - **Sample walk routes through PROJ.** Placing samples with the OSM spherical approximation put them metres off the UTM meshes and reported 91 phantom holes. `/tmp` is not shared between tool calls here either — regenerate instead of saving intermediate files there.
 - **3DEP cannot resolve kerbs.** Sharpest break near the kerb line is 0.09–0.12 m/m, a gutter transition, not a 0.15 m upstand. Kerb height stays a stated assumption.
 - **Building interiors are not ground.** Points inside the hero footprint returned 114.5–117.1 m — structure, not terrain. Excluded from the relief figure.