- Extract model loading from generate()/edit() into VnAssetsSession class
- Session eagerly loads SDXL + Qwen Image Edit at construction (28s, once)
- Both models held in GPU memory across calls; generate()/edit() reuse them
- generate.py and edit.py become thin wrappers (backwards compatible CLI)
- Context manager (with VnAssetsSession(...) as vna:) for library use
- Metadata backwards-compatible: all fields preserved including lora_load_s
- load_time_s now reflects total session construction, amortized across calls
- Add performance stats for edit path (Qwen Image Edit + Lightning LoRA)
- Benchmark matmul fallback (86.8s) vs flash attention (53.3s, 1.63x speedup)
- Session vs cold start comparison: 2 ops save one 28s load, 5 edits save 112s
- Flash attention via TORCH_ROCM_AOTRITON_ENABLE_EXPERIMENTAL=1 documented
