statusline: a didbot session shows no agent until it first runs vibescrobble #76

A session learns its DID from didbot's hook on its first tool call, and the vibescrobble hook records it only from a vibescrobble … --as <DID> command. Until then vibescrobble statusline shows only the live count. Ask the didbot agent daemon at SessionStart which DID the session has, if didbot exposes that, or have didbot write it where the statusline reads.