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.

MEMORY.md

@@ -359,3 +359,23 @@ Scope: facts and traps that cost time to establish. Planned work lives in [TODO.
   45 cm MaxStepHeight, so not blocking.
 - Kerb height finalised at 0.15 m modelled / 0.13 m built (6 in LA standard; DEM
   and photos can't resolve finer).
+
+## 2026-11-09 — Mapbox building data as a second height source
+
+- `Geo/tools/mapbox_buildings.py` (new, stdlib `urllib`) Tilequeries
+  `mapbox.mapbox-streets-v8` layer `building` at every building centroid in the
+  extract and merges the answer with our OSM height + source. Token comes from
+  `MAPBOX_ACCESS_TOKEN` in the ignored `.env`; responses cache to
+  `Geo/raw/mapbox-cache/`.
+- **Mapbox terms restrict persisting/redistributing their data**, so `.gitignore`
+  now covers `/Geo/raw/mapbox-cache/` and `/Geo/verification/*mapbox*`. The tool
+  also refuses to cache a response that contains the token.
+- **First run (72 buildings): 58 match, 5 close, 3 disagree, 6 non-building.**
+  - It independently classifies our roof/canopy/shelter volumes as `roof`/
+    `shelter` — corroborating the `0.1.2` finding that they are not buildings.
+  - Remaining disagreements are untyped `building=yes`/`apartments` rear
+    structures where our fallback guess (2 × 3.2 m = 6.4 m) meets Mapbox's 3.0 m.
+  - Every "close" case is a `building:levels × 3.2 m` building where Mapbox is
+    **0.6 m lower per 6 levels** → Mapbox implies **3.1 m per level**, not 3.2.
+    Worth revisiting `LEVEL_HEIGHT` if a measured storey height ever lands.
+  - Its query API surface: `height`, `min_height`, `type`, `extrude` per polygon.