feat(hero): fluting and a recessed motto band; placement gets one source of truth

Hero detail:
- Fluting: 20 grooves per column as thin shadow-tone cylinders set into the shaft
  (120 pieces) rather than boolean cuts - readable in silhouette and grazing light
  at a fraction of the cost.
- Motto band: real recess with a moulded surround 6 cm proud and the panel 12 cm
  behind, replacing the 8 cm dark stripe.
  Hero 148 parts/3044 tris -> 271/5492, still 14.50 m.

Placement bug this exposed (a real one, invisible in a render):
- ue_hero_facade_import.py carried its own hero position (-12024.5, -1450) from
  before the 0.1.0 frontage fix, so running the importer alone moved the hero 13 m
  east and onto the north side of the boulevard. Only symptom: the reference score
  fell 0.69 -> 0.56 and the 3x3 composition correlation flipped +0.54 -> -0.08.
- New Tools/ue_placement.py is the single source of truth (hero position, verified
  frontage spans, span validators). Both the importer and the demo builder use it;
  the import asserts the staged span and logs PLACEMENT ERROR otherwise.
- 11 new tests, including one that fails if the stale literal returns. 78 total.

Spawn-view score recovered to 0.72 (best yet); screenshots verified 4/4, packaged QA
all PASS.

TODO.md

@@ -18,7 +18,7 @@ The `0.1.4` kit, materials and theatre trim are signed off; these are the geomet
 ### Patch tasks
 
 - [A] **Retail neighbours (6822 Budget, 6806–6820, 6800 Lee Drug) from their own references.** **Started 2026-11-09.** Fetched the one usable reference Commons holds for this run — `Art/reference/retail-neighbours/01-lee-drug-and-neighbor.jpg` (Gb321, CC BY-SA 4.0, 1920×953) — which shows 6800 **and** its neighbour at street level; the vision pre-check confirmed shopfronts and parapets are visible. The 18-frame theatre set cannot stand in for these façades, and Commons has nothing else for 6822 or 6806–6820, so per-building references for those two remain the blocker. **Kit layout fixed while here:** bay count was `round(width / 4.96)`, which gave 6922 thirteen bays across 65.8 m (a window every 4.96 m on a 37 m block) and left bare wall under the cornice; bays are now capped at 9 with the module widened, and the storey spread fills the available height (6922 9 × 11, 6806 7 × 3, 6800 4 × 3, theatre 8 × 6).
-- [ ] **Hero façade: fluting and the motto band as geometry.** The colonnade is plain cylinders and the motto/medallions are flat panels; both are legible in the reference photography.
+- [x] **Hero façade: fluting and the motto band as geometry.** **Done 2026-11-09.** Fluting: 20 grooves per column (thin shadow-tone cylinders set into the shaft, 120 pieces) instead of boolean cuts — it breaks the flat highlight at a fraction of the poly cost. Motto band: a real recess now, with a moulded surround standing 6 cm proud and the panel set 12 cm behind it, replacing the 8 cm dark stripe. Hero is 271 objects / 5 492 tris (from 148 / 3 044) and still 14.50 m. **En route it exposed a placement bug:** `ue_hero_facade_import.py` carried its own stale hero position `(-12024.5, -1450)` from before the `0.1.0` frontage fix, so running the importer alone moved the hero 13 m east and onto the north side — invisible in a render, and it dropped the reference score from 0.69 to 0.56. Placement now lives in `Tools/ue_placement.py` with span validators, asserted after every import (`span ok: X -14644..-12028`), and the spawn-view score recovered to **0.72**.
 - [ ] **Blosm blockout cleaning pass.** Roofs and facades remain untextured volumes and the `setupScript` styles stay unused; with the kit carrying the elevations, this is now cleanup rather than a second façade system.
 - [ ] **Re-measure 1440p performance** with 625 kit actors and 8 generated textures in the map. `0.1.0` measured 414 fps average, so there is headroom, but it has not been re-run since.
 - [ ] Tag `v0.1.5` and write `CHANGELOG.md` entry; then remove this section.