Function emit_coproc_soc_testbench 

pub fn emit_coproc_soc_testbench() -> String

Emit the self-checking testbench. The expected result registers are DERIVED from run_core (not hand-typed): the tb decodes the UART TX stream, reconstructs the sync byte + 128 payload bytes, and checks each MSB-first byte against the model’s retired R2..R5. PASS iff every byte matches — the software≡RTL proof over the serial framing.