feat(facades): 0.1.6 retail frontage first pass — Lee Drug and 6806-6820

Models the two retail buildings beside the hero from their own photograph rather
than the generic kit: bronze cornice, mural row, lettering band, stepped Deco
parapet and rounded corner tower on 6800 Lee Drug; burgundy fascia, pilasters,
white-framed windows and banded parapet on 6806-6820. Reference analysis written
before any geometry (Art/blender/retail/ref-analysis.md), every unmeasured
proportion carried into the part report as an assumption.

6822 Budget is deferred, not guessed: no photograph of it exists and the 6.0 x 5.5 m
sliver cannot be read out of the neighbour shot.

Pipeline fixes found on the way:
- render_screenshots.sh called ./Engine/... for the capture step while every
  commandlet used the absolute path; set -e killed the script at 127 *after* the
  maps were rebuilt, so screenshots silently stayed a day old.
- the facade kit applies to every Frontage_*/North_* actor, so it pasted its own
  language over the new modelled facades; it now skips them, and the trim stages as
  RetailTrim_*.
- pure bay arithmetic moved to Tools/_common.py so it is unit-testable without
  Blender (4 new tests, 82 total pass).

Known gaps recorded in Screenshots/README.md, not hidden: the parapet reads as a
blank band, murals and lettering do not resolve at review distance, the tower is a
plain cylinder, and the review camera crops the east end.

Tools/ue_apply_facade_kit.py

@@ -235,9 +235,17 @@ def main() -> None:
             removed += 1
     log(f"cleared {removed} previous kit actors")
 
+    # The kit is the fallback for buildings that have nothing but a blockout. These
+    # two are modelled from their own photograph in 0.1.6
+    # (Tools/retail_frontage_build.py); pasting the generic kit over them put a
+    # second, contradicting facade language on the same wall.
+    MODELLED = ("Frontage_SM_LeeDrug_6800", "Frontage_SM_Hollywood_6806")
     targets = [a for a in unreal.EditorLevelLibrary.get_all_level_actors()
-               if a.get_actor_label().startswith(("Frontage_", "North_"))]
-    log(f"frontage actors: {len(targets)}")
+               if a.get_actor_label().startswith(("Frontage_", "North_"))
+               and a.get_actor_label() not in MODELLED]
+    skipped = [a.get_actor_label() for a in unreal.EditorLevelLibrary.get_all_level_actors()
+               if a.get_actor_label() in MODELLED]
+    log(f"frontage actors: {len(targets)} (kit skipped on modelled facades: {skipped})")
     total = 0
     for actor in targets:
         total += apply_to_actor(actor, kit, materials)