Establish the 0.9.4 NPC visual baseline

Add a neutral 48-frame character contact sheet, acceptance criteria and ranked baseline gaps, plus repeatable sheet/comparison tooling. No character GLB or runtime mesh changes.

tools/test_npc_baseline.py

@@ -0,0 +1,28 @@
+import os
+import tempfile
+import unittest
+from pathlib import Path
+
+import npc_baseline
+
+
+class NpcBaselineTests(unittest.TestCase):
+    def test_expected_files_cover_all_variants_and_views(self):
+        rows = npc_baseline.expected_files()
+        self.assertEqual(len(rows), 48)
+        self.assertEqual({row[0] for row in rows}, set(npc_baseline.VARIANTS))
+        self.assertEqual({row[1] for row in rows}, set(npc_baseline.VIEWS))
+        self.assertEqual(len({row[2] for row in rows}), 48)
+
+    def test_latest_capture_prefers_the_full_stem(self):
+        with tempfile.TemporaryDirectory() as tmp:
+            folder = Path(tmp)
+            (folder / "npc_casual__front.png").write_bytes(b"old")
+            newer = folder / "npc_casual__front-v2.png"
+            newer.write_bytes(b"new")
+            os.utime(newer, (2_000_000_000, 2_000_000_000))
+            self.assertEqual(npc_baseline.latest_for(folder, "npc_casual__front"), newer)
+
+
+if __name__ == "__main__":
+    unittest.main()