ModelTranslator: 终审 Minor——sidecar 用 finally 清理 + average_islands_scale 补捕 TypeError

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Tools/ModelTranslator/model_decimate.py

@@ -40,10 +40,12 @@ def main():
             with open(s["uv_polys"], encoding="utf-8") as fp:
                 polys = _json.load(fp)
             render_uv_png(polys, s["uv_preview"])
-            os.remove(s["uv_polys"])
             print("  UV 观察图: %s" % s["uv_preview"])
         except Exception as e:
             print("  [警告] UV 观察图渲染失败：%s" % e)
+        finally:  # sidecar 是内部临时文件，无论渲染成败都清掉
+            if os.path.exists(s["uv_polys"]):
+                os.remove(s["uv_polys"])
     for w in s["warnings"]:
         print("  [警告] %s" % w)