Move benchmark scripts into benchmarks/ subdir

- benchmarks/run_benchmark.py (was run_benchmark.py)
- benchmarks/run_voice_benchmark.py (was run_voice_benchmark.py)
- Scripts use Path(__file__).parent so paths resolve correctly in subdir
- .gitignore updated: ignore benchmarks/benchmark.json,
  results_latest.json, voice_results*.json, voice_audio/

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.gitignore

@@ -2,5 +2,7 @@ __pycache__/
 *.pyc
 logs/*.jsonl
 adolf_tuning_data/voice_audio/
-benchmark.json
-results_latest.json
+benchmarks/benchmark.json
+benchmarks/results_latest.json
+benchmarks/voice_results*.json
+benchmarks/voice_audio/