Function validate_answer_feedback_shape 

pub fn validate_answer_feedback_shape(
    mode: ClassifierTrainingMode,
    feedback: [u32; 3],
    reference: [u32; 3],
    output_shapes: &[[u32; 3]],
    class_count: u32,
) -> Result<(), String>

Answer feedback must match the classifier output.

Kernel mode compares the class area. Scanner mode compares each detection twin (W×H×1, class as potential) or accepts a whole-image class of class_count channels. With no twin yet, the mask is that output.