feat(geo): cross-check block heights against Mapbox building data

New Geo/tools/mapbox_buildings.py (stdlib urllib) Tilequeries
mapbox-streets-v8 / layer building at each building centroid and merges
height/min_height/type with our OSM height + source (tag > levels > guess,
reusing block_height_report.classify_height). Reports matches, close calls,
disagreements (sorted worst first), our-only and mapbox-only cases, and writes
optional JSON.

First run over 72 buildings: 58 match, 5 close, 3 disagree, 6 non-building.
- Mapbox independently classifies our roof/canopy/shelter volumes as roof,
  canopy or shelter -> corroborates the 0.1.2 finding.
- The 3 disagreements are rear building=yes/apartments structures rendering at
  our 2-level guess (6.4 m) vs Mapbox's 3.0 m.
- Every levels x 3.2 m building is ~0.6 m per 6 levels taller than Mapbox
  implies, i.e. Mapbox suggests 3.1 m per level. Recorded, not applied.

classify_height() now also treats building=canopy as a non-building volume
(found by this cross-check), with tests.

Data handling: Mapbox terms restrict persisting/redistributing their data, so
.gitignore covers Geo/raw/mapbox-cache/ and Geo/verification/*mapbox*; the tool
refuses to cache a response containing the token, and the token is never written
to the cache, report or JSON. Token comes from the ignored .env.

Also: 17 new tests (29 total) for the compare/nearest/centroid/render helpers
and the canopy rule; Geo/README inventory row; architecture 05 + architecture.md
tools table updated per the new upkeep rule.

Geo/tools/block_height_report.py

@@ -29,8 +29,13 @@ def classify_height(tags, level_height=LEVEL_HEIGHT):
     rule and the "height tag beats levels beats guess" order are the parts that
     actually decide what the blockout should render.
     """
-    if tags.get("building") == "roof" or tags.get("amenity") == "shelter":
-        kind = "roof" if tags.get("building") == "roof" else "shelter"
+    # Not building volumes: elevated roof/canopy structures and transit shelters.
+    # Found by cross-checking against Mapbox's building data
+    # (Geo/tools/mapbox_buildings.py), which returns roof/canopy/shelter for the
+    # same footprints instead of a storey count.
+    building = tags.get("building")
+    if building in ("roof", "canopy") or tags.get("amenity") == "shelter":
+        kind = building if building in ("roof", "canopy") else "shelter"
         return 0.0, f"not a building volume ({kind})"
     if tags.get("height"):
         return float(tags["height"]), "height tag"