Function try_emit_seq_datapath_verilog 

pub fn try_emit_seq_datapath_verilog(
    name: &str,
    df: &DecisionFabric,
) -> Result<String, LoweringError>

Graceful entry to a single sequenced decision datapath: Ok(rtl) when every cell is register-only, or Err(StatePlaneUnlowered) for a heap-reading fabric (which belongs on the state-plane emitter). The typed companion to emit_seq_datapath_verilog.