fix(hero): the albedo renders - two blockers, both at the map level

The generated ashlar albedo never showed for two reasons that had nothing to do with the material graph,
which was verified correct the whole time (TextureSampleParameter2D -> Multiply -> Base Color, colour sampler,
texture set, 6x UV tiling):

1. **The map overrode every hero slot.** The generic per-slot material pass in ue_build_demo_map.py assigned
   the facade KIT's flat stone to every actor whose slot names looked like stone, banner, glass - including
   Hero_Facade. Whatever the import authored was replaced at map build time. The hero is now excluded and gets
   its own materials.
2. **Mesh slot assignment does not persist.** Assigning to mesh.get_editor_property('static_materials') returns a
   copy; after a reload the mesh still pointed at the original imported materials (measured twice). Component
   level overrides do persist in the saved map, so apply_hero_materials() sets them in both builders.

The elevation now renders as coursed, grainy warm limestone with banners, window bays and recessed portals.

Rows 4-6 re-rendered and pending review; the comparison plate is regenerated. Still missing against the
reference: carved inscription, medallion relief, banner lettering, crimson banner tone. The two-model judge
returns no/no (0.90/0.95) - it wants the text and detail that are still absent, which is at least the right
complaint this time.

Screenshots/README.md

@@ -16,9 +16,9 @@ Both capture passes are produced by [`Tools/review/render_screenshots.sh`](../To
 | 1 | ReviewMap | ![character feet](review/review-character-feet.png) | [x] | approved |
 | 2 | ReviewMap | ![character](review/review-character.png) | [x] | approved |
 | 3 | ReviewMap | ![ground contact](review/review-ground-contact.png) | [x] | approved |
-| 4 | ReviewMap | ![hero facade front](review/review-hero-facade-front.png) | [ ] | warm sandstone with ashlar coursing, banners, window bays and recessed portals now render; still missing: carved inscription, medallion relief, crimson banner tone, window grilles read too dark |
-| 5 | ReviewMap | ![hero facade oblique](review/review-hero-facade-oblique.png) | [ ] | warm sandstone with ashlar coursing, banners, window bays and recessed portals now render; still missing: carved inscription, medallion relief, crimson banner tone, window grilles read too dark |
-| 6 | ReviewMap | ![hero portals](review/review-hero-portals.png) | [ ] | warm sandstone with ashlar coursing, banners, window bays and recessed portals now render; still missing: carved inscription, medallion relief, crimson banner tone, window grilles read too dark |
+| 4 | ReviewMap | ![hero facade front](review/review-hero-facade-front.png) | [ ] | re-rendered with the generated ashlar albedo: the stone now carries coursing and grain, banners, window bays and recessed portals all read; still missing the carved inscription, medallion relief, banner lettering and a crimson banner tone |
+| 5 | ReviewMap | ![hero facade oblique](review/review-hero-facade-oblique.png) | [ ] | re-rendered with the generated ashlar albedo: the stone now carries coursing and grain, banners, window bays and recessed portals all read; still missing the carved inscription, medallion relief, banner lettering and a crimson banner tone |
+| 6 | ReviewMap | ![hero portals](review/review-hero-portals.png) | [ ] | re-rendered with the generated ashlar albedo: the stone now carries coursing and grain, banners, window bays and recessed portals all read; still missing the carved inscription, medallion relief, banner lettering and a crimson banner tone |
 | 7 | ReviewMap | ![npc prefab](review/review-npc-prefab.png) | [x] |  |
 | 8 | ReviewMap | ![overview](review/review-overview.png) | [x] | approved |
 | 9 | ReviewMap | ![player placement](review/review-player-placement.png) | [x] | approved |