Fix NameError in list_search_commits final-cache write

Local var is final_cache (line 754) but write at line 801 referenced
cache_file, which only exists in sibling list_prs_and_issues. Would
crash on first non-cached run in full mode, preventing search_commits
cache from ever being saved.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: pirate

generate_stats.py

@@ -798,7 +798,7 @@ def query(date_filter: str) -> list[dict]:
         all_items.extend(items)
         time.sleep(0.3)
     CACHE_API.mkdir(parents=True, exist_ok=True)
-    cache_file.write_text(json.dumps(all_items))
+    final_cache.write_text(json.dumps(all_items))
     return all_items