feat(hero): Ionic base and abacus, medallions onto the parapet face

Detail pass on the hero, all verified by measuring the built mesh:

- Column base moulding: a 1.36 m wide, 0.22 m tall cylinder at each shaft foot
  (2.00-2.22 m). The shaft previously started straight off the square pedestal,
  so the base never read in silhouette.
- Abacus: a 1.30 m square, 0.14 m thick slab over each capital. It takes the top
  of the capital zone, so the colonnade still ends at 9.70 m and the 53.1 %
  proportion is unchanged.
- Medallions fixed: they were built with the Z-axis cylinder helper, so the two
  'discs' were pancakes lying flat on the parapet coping (1.1 x 1.1 x 0.02,
  z 14.02-14.04). New disc_on_wall() helper rotates the cylinder 90 deg about X;
  they now stand 1.1 m across on the parapet face (y -1.32..-1.28,
  z 13.05..14.15).

Hero rebuilt (95 parts, 2420 tris, still 14.50 m), re-imported, DemoMap rebuilt,
screenshot set re-rendered. Part report records the new dims and their assumption
notes. Screenshots README notes the detail pass.

TODO.md

@@ -16,7 +16,7 @@ Suggested blender skills: **references** (reference-image-match and visual-match
 ### Patch tasks - active - 01a1b26b-3c94-707f-9665-2f6b4a79b564 (branch `scale-facade-0.1.2`)
 
 - [x] Correct building scale and street proportions flagged against references. **Mapbox adopted 2026-11-09.** `Geo/tools/mapbox_buildings.py` merges our OSM heights with Mapbox's building data for the same footprints; after adopting its two findings the cross-check reports **66 match, 6 non-building, 0 disagreements**. Adopted: **`LEVEL_HEIGHT` 3.2 → 3.1 m** (`block_height_report.py`, and the Blosm `--level-height` default), plus explicit `HEIGHT_OVERRIDES` (3.0 m) for the three rear `building=yes`/`apartments` structures Mapbox gives as single-storey. Blockout regenerated, frontage re-exported/re-imported, DemoMap rebuilt; packaged `-qaselftest` all PASS. Measured effect: 6922 42.1 → 39.1 m, El Capitan Theatre 20.0 → 20.5 m (both now ~1.9 m above their table height = roof mass).
-- [ ] Refine hero façade details where reference photography shows discrepancies. **Started 2026-11-09:** built `Tools/facade_detail_concepts.py`, which generates architectural detail plates from the local reference photographs with an image model (`--list` free, `--all` generates, sidecars + `-vN` no-overwrite, output gitignored). Six **frontal building** studies generated locally under `Art/reference/facade-details/` (whole elevation, entrance in its facade, building with neighbours, pavement view, three-quarter, theatre frontage) — rephrased on owner instruction to show the building/entrance/neighbours rather than close-up detail crops. **First fix from the measurement pass:** window panes were 1.44 m in front of the wall (ahead of the columns) and now sit on the wall plane behind the colonnade. Remaining: use the plates to correct the capital/base profiles and the medallion/cornice detail.
+- [ ] Refine hero façade details where reference photography shows discrepancies. **Started 2026-11-09:** built `Tools/facade_detail_concepts.py`, which generates architectural detail plates from the local reference photographs with an image model (`--list` free, `--all` generates, sidecars + `-vN` no-overwrite, output gitignored). Six **frontal building** studies generated locally under `Art/reference/facade-details/` (whole elevation, entrance in its facade, building with neighbours, pavement view, three-quarter, theatre frontage) — rephrased on owner instruction to show the building/entrance/neighbours rather than close-up detail crops. **First fix from the measurement pass:** window panes were 1.44 m in front of the wall (ahead of the columns) and now sit on the wall plane behind the colonnade. **Detail pass 2026-11-09 (all measured on the built mesh):** added an Ionic base moulding (1.36 m × 0.22 m) at each shaft foot and a square abacus (1.30 m × 0.14 m) over each capital, taking the abacus out of the capital zone so the colonnade still ends at 9.70 m; re-oriented the two parapet medallions, which were flat discs lying on the coping (1.1 × 1.1 × 0.02 in the wrong axes) instead of discs on the parapet face; window panes moved onto the wall plane. Hero is now 2 420 tris across 95 parts, still 14.50 m. Cornice/dentil profile refinement remains.
 - [x] **Replace the placeholder heights.** **Resolved 2026-11-08 — they were never unknown buildings.** The three "guessed" ways are not building volumes at all: `1360755125` and `1360755126` are `building=roof` at `layer=1` (elevated canopies) and `1417995292` is `amenity=shelter` / `shelter_type=public_transport` (a transit shelter). The report defaulted them to "2 levels × 3.2 m" and produced the bogus 6.4 m. `Geo/tools/block_height_report.py` now classifies roof/shelter explicitly and reports **0 guessed heights**: all 15 block volumes have a real `height` tag, a `building:levels` derivation, or are correctly excluded as non-building volumes. No photograph measurement was needed, and no frontage building was affected.
 - [x] Resolve the remaining unknown on the hero: the colonnade currently occupies about 45 % of the height against roughly 50–60 % in the photographs. Fix the vertical proportions. **Fixed 2026-11-09.** Measured baseline: colonnade (columns + capitals) 6.90 m of the 14.50 m envelope = **47.6 %**, because the entablature (3.40 m) and parapet (2.20 m) left only 7.90 m for the order. Thinned both to **3.00 m** and **1.80 m** (`Tools/hero_facade_build.py`), which lifts the colonnade to **7.70 m = 53.1 %** — inside the photographed 50–60 % band, with the 14.50 m envelope, the motto band and the medallions unchanged in position relative to the parapet. Hero rebuilt, re-imported (bounds 2604 × 1257 × 1450 cm) and re-rendered.
 - [ ] Tag `v0.1.2` and write `CHANGELOG.md` entry; then remove this section.