三芯片合并:AX620E/AX637 升级 encoder+decoder 全 NPU,新增新一代 SDK;AX650 保持老 SDK

feat: add AX620E and AX637 support (encoder NPU + decoder ONNX fallback)

feat: add board-generated audio samples, fix attn_mask bug, dp.onnx IR9

feat: remove torch dependency, use onnxruntime + numpy

fix: remove duplicate axmodels, fix model paths, add config.json for download tracking

Inflect-Micro-v2 TTS: AX650 NPU3, U16 AXMODEL