feat(hero): one-command iteration loop, first judged pass, comparison plates

Tools/hero_iterate.sh runs the whole chain - chmod the Blender files, build, import, render, judge, plate -
and fails loudly at each step with its log under /tmp/gigline. Tools/hero_compare.py builds the side-by-side
plate (reference | rendered, one height, labelled); two are committed for review.

This pass: the stone is warmer in Blender (0.66/0.60/0.48 against the near-white blockout) and the banners are
1.35 x 6.2 m hung from 7.2 m, matching the reference proportion instead of the 1.55 x 5.4 that sat too low and
too fat.

Iteration 1 judge verdict, confidence 0.9: lacks warm sandstone, lacks fluted column detail, banners wrong,
no doorways, no inscription or medallions. Checked against the plate, two of those are wrong (120 flute
strips exist and cast shadows; three 1.2 m deep doorways with steps exist and read black) and three are real.
The split is recorded in TODO.md with the next action for each - the important one being that the stone colour
must change in the UE material (ue_hero_facade_import.py), not in the Blender material, which the render does
not use.

Tools/hero_facade_build.py

@@ -129,8 +129,10 @@ def build():
     for obj in list(bpy.data.objects):
         bpy.data.objects.remove(obj, do_unlink=True)
 
-    stone = make_material("M_Facade_Stone", (0.78, 0.74, 0.66, 1.0), 0.85)
-    stone_dark = make_material("M_Facade_StoneShadow", (0.62, 0.59, 0.53, 1.0), 0.85)
+    # Warm limestone, sampled from 02-masonictemple01.jpg: the reference is a yellow-grey sandstone,
+    # nowhere near the near-white the blockout used.
+    stone = make_material("M_Facade_Stone", (0.66, 0.60, 0.48, 1.0), 0.82)
+    stone_dark = make_material("M_Facade_StoneShadow", (0.52, 0.47, 0.38, 1.0), 0.85)
     glass = make_material("M_Facade_GlassDark", (0.05, 0.06, 0.07, 1.0), 0.25)
     banner = make_material("M_Facade_Banner", (0.66, 0.06, 0.05, 1.0), 0.9)
 
@@ -340,8 +342,10 @@ def build():
     # --- banners -----------------------------------------------------------
     # Three vertical event banners hung from the column line, as the recordings show.
     for i, x in enumerate(portal_xs, start=1):
-        cube(f"Hero_Banner_{i}", x, -1.05, 7.9, 1.55, 0.06, 5.4, banner)
-    note("Hero_Banner_x3", (1.55, 0.06, 5.4), "photographs: JIMMY KIMMEL LIVE banners on the column line")
+        # The reference banners hang from just below the capitals down to the portal heads:
+        # 6.2 m tall and 1.35 m wide, not the 5.4 x 1.55 blockout that sat too low and too fat.
+        cube(f"Hero_Banner_{i}", x, -1.05, 7.2, 1.35, 0.06, 6.2, banner)
+    note("Hero_Banner_x3", (1.35, 0.06, 6.2), "photographs: JIMMY KIMMEL LIVE banners on the column line")
 
     # --- windows -----------------------------------------------------------
     # Two ranks of windows between the columns and behind the colonnade.