hero: make the portals real recesses and land the facade on Z 0

The portal detail shot failed for a modelling reason, not a camera reason: the
doors were 0.1 m panels on a solid plinth, so they read as shading. The plinth is
now four piers plus a lintel band, with a 1.2 m reveal, stone jambs and lintels
standing 0.10 m proud and three mullions per opening. review-06 frames them from
8 m at eye height.

Two defects fixed while doing it: the jamb boxes hung 0.15 m below the pavement,
so the facade imported with min Z -15 cm; and a rebuild run against a read-only
.blend silently skipped the save, which is why screenshots kept showing the old
geometry.

Tools/ue_build_review_map.py

@@ -172,7 +172,11 @@ try:
         # targets the portal sill rather than the centre of the elevation.
         # Standing 25 m out at eye height frames the whole elevation, which is what
         # the portal detail needs: the portals are small against a 14.5 m façade.
-        ("hero-portals", unreal.Vector(hero_x + 150, -4000, 170), unreal.Vector(hero_x + 150, hero_y, 420)),
+        # On the pavement in front of the flight: a pedestrian's own eye line, the
+        # angle the photographs that established the portals were taken from.
+        # eye height at 8 m: fills the frame with the three doorways, the flights and
+        # the plinth, which is what "portal detail" means here.
+        ("hero-portals", unreal.Vector(hero_x + 100, -2250, 170), unreal.Vector(hero_x + 100, hero_y, 230)),
         # straight on from the north sidewalk; the building body spans Y -1443..+250
         ("hero-facade-front", unreal.Vector(hero_x + 200, -3200, 420), unreal.Vector(hero_x, hero_y + 400, 760)),
         # oblique from the north-west, reading the colonnade in depth