Constant MIN_COMMITMENTS_PER_SSA_COMMIT_MSG 

const MIN_COMMITMENTS_PER_SSA_COMMIT_MSG: usize = _; // 26usize

Conservative lower bound on how many coefficient commitments fit into one SsaCommit message.

Mirrors the sizing in SsaClientCommitmentMessage::new_multiple: payload minus the fixed prefix (ssa_index + coefficient_index + num_polys + the Start header) and minus a generous allowance for the CBOR-encoded session id, divided by the per-entry cost (PolynomialIndex + one serialized group element). Using a lower bound here means the derived message count is an over-estimate, which is the safe direction for sizing a queue.

The commitment proof of knowledge is subtracted as well. Every message carries it, since every message is a constant-term message.