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.

Tools/tests/test_block_height_report.py

@@ -37,6 +37,12 @@ class ClassifyHeightTest(unittest.TestCase):
         self.assertEqual(height, 0.0)
         self.assertIn("not a building volume (roof)", source)
 
+    def test_canopy_is_not_a_building_volume(self):
+        # building=canopy at layer=1, found by the Mapbox cross-check.
+        height, source = bhr.classify_height({"building": "canopy", "layer": "1"})
+        self.assertEqual(height, 0.0)
+        self.assertIn("not a building volume (canopy)", source)
+
     def test_transit_shelter_is_not_a_building_volume(self):
         height, source = bhr.classify_height(
             {"building": "yes", "amenity": "shelter", "shelter_type": "public_transport"})