- Cache Ort::MemoryInfo and I/O names in gunshot_classifier (avoid per-inference alloc)
- Reuse single FeatureExtractor across all files in demo_offline
- Add per-file and total inference timing to demo_offline
- Remove third_party/kiss_fft directory (fully replaced by inline FFT)
- Update fft_utils.h comments to remove stale kiss_fft references
- Verify 20/20 validation accuracy maintained, ~160ms avg per file
