Function tensor_plan 

pub fn tensor_plan(
    name: &str,
    mixer: MixerKind,
    _mlp: MlpKind,
    config: &ModelConfig,
) -> (TpShardKind, usize, usize)

2026-09-25: (kind, full_out, full_in) for one checkpoint key. A key the plan does not name is Replicated.