feat: template attempt unknown changes

Author: FunMelon

openevolve/prompt/sampler.py

@@ -247,7 +247,7 @@ def _format_evolution_history(
 
         for i, program in enumerate(reversed(selected_previous)):
             attempt_number = len(previous_programs) - i
-            changes = program.get("metadata", {}).get("changes", "Unknown changes")
+            changes = program.get("metadata", {}).get("changes", self.template_manager.get_fragment("attempt_no_changes"))
 
             # Format performance metrics using safe formatting
             performance_parts = []

openevolve/prompts/defaults/fragments.json

@@ -18,6 +18,7 @@
   "no_feature_coordinates": "No feature coordinates",
   "artifact_title": "Last Execution Output",
   "diverse_programs_title": "Diverse Programs",
+  "attempt_unknown_changes": "Unknown changes",
   "attempt_all_metrics_improved": "Improvement in all metrics",
   "attempt_all_metrics_regressed": "Regression in all metrics",
   "attempt_mixed_metrics": "Mixed results",