CuasDnnInfer reads N (temporal frame count) from the model's input
shape [B,N,H,W] and exposes getNFrames(); the constructor arg is now
only a fallback hint. CuasDetectRT uses dnn.getNFrames() instead of the
hardcoded 8, so an 8- vs 9-frame ONNX swaps purely by changing
curt_dnn_model (N follows automatically).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>