• Sign a ChannelMessage envelope with the sender's primary-claim key.

    The signature covers dacs-channelmsg:v1: || sha256(JCS(envelope w/o signature)). Transport-level wrappers MUST NOT alter the bytes returned here. Throws if unsigned.sender is not a demos: ClaimReference or does not match the connected wallet — preserves the in-channel-signer == on-chain-party invariant.

    Parameters

    Returns Promise<ChannelMessage>