Function batch_commitment_words 

pub fn batch_commitment_words(
    epoch: b64,
    batch_id: b64,
    root: [b8; 32],
) -> [b64; 8]

Build the Ed25519 fixed-64 message in RHDL, without hashing on the host.

The background scheduler supplies a completed 128-key Merkle root and its durably allocated namespace. The result maps directly to the Ed25519 core’s SignRequest.message.words. This adapter is pure packing: it neither signs nor validates a certificate, and it does not authorize cache admission.

Inputs: epoch and batch_id (64 bits each), root (32 bytes, in hash output order). Output: eight 64-bit words; word i holds envelope bytes 8i..8i + 8 in little-endian order. Timing: purely combinational (no registers, zero cycles of latency); it is wires plus constants.