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/visual_targets.json

@@ -48,6 +48,18 @@
         "Art/reference/north-chinese/01-grauman-s-chinese-theatre-by-carol-highsmith.jpg"
       ],
       "expect": "The two north-side buildings (TCL Chinese Theatre, Madame Tussaud's) seen from across Hollywood Boulevard, full height in frame, daylight"
+    },
+    {
+      "name": "demo-retail-frontage",
+      "shot": "Screenshots/demo/review-demo-retail-frontage.png",
+      "size": [
+        1920,
+        1080
+      ],
+      "references": [
+        "Art/reference/retail-neighbours/01-lee-drug-and-neighbor.jpg"
+      ],
+      "expect": "The retail run beside the hero from across the street: 6800 Lee Drug's bronze cornice, mural row and stepped parapet next to 6806-6820's pilasters and window storey, daylight"
     }
   ]
 }