merge: bring main (v0.1.6) into anim-body-0.2.0

Conflicts resolved by union, not by picking a side:

- AGENTS.md keeps the stronger visual-review rule (README updated with every visual
  change; a stale section is a defect).
- render_screenshots.sh keeps the absolute engine path from main and adds
  -thirdperson from this branch - both were needed and neither alone worked.
- Screenshots/README.md now lists six shots, retail and third-person both embedded;
  the known-issues tables merged, with the animation defect and unproven camera
  collision added to main's rows.
- visual_targets.json carries both expectations.
- Architecture docs: ADR-8 (realistic buildings) and ADR-9 (third-person body) both
  present and in numeric order; ADR-8 was mis-placed before the Quality Requirements
  heading in the combined document by an earlier edit, now fixed.
- Binary conflicts resolved to main's content, since the retail trim only exists
  there.

Checks: 82 tool tests, prettier clean, six embeds resolve.

Tools/tests/test_retail_frontage.py

@@ -0,0 +1,32 @@
+"""Tests for the pure layout helper in Tools/retail_frontage_build.py.
+
+The builder itself needs Blender; `bay_centres` does not, so the bay rhythm the
+façade depends on is checkable without starting Blender or Unreal.
+"""
+
+import unittest
+
+from Tools._common import bay_centres
+
+
+class BayCentreTests(unittest.TestCase):
+    def test_centres_stay_inside_the_margins(self):
+        centres = bay_centres(-33.20, -14.37, margin=1.2)
+        self.assertGreaterEqual(min(centres), -33.20 + 1.2 - 1e-9)
+        self.assertLessEqual(max(centres), -14.37 - 1.2 + 1e-9)
+
+    def test_bays_are_evenly_spaced(self):
+        centres = bay_centres(-66.08, -33.07, margin=1.0)
+        steps = {round(b - a, 6) for a, b in zip(centres, centres[1:])}
+        self.assertEqual(len(steps), 1, f"uneven bay spacing: {steps}")
+
+    def test_bay_count_is_the_round_of_span_over_bay(self):
+        # 33.01 m frontage, 1.0 m margin each end -> 31.01 m -> 14 bays at 2.2 m.
+        self.assertEqual(len(bay_centres(-66.08, -33.07, margin=1.0)), 14)
+
+    def test_degenerate_frontage_returns_nothing(self):
+        self.assertEqual(bay_centres(0.0, 1.0, margin=1.0), [])
+
+
+if __name__ == "__main__":
+    unittest.main()