Function begin 

pub fn begin(
    store: &Talks,
    cfg: &Config,
    repo: PathBuf,
    agent: Option<&str>,
) -> Result<Talk>

Open a conversation. Unlike crate::chat::start this takes no agent turn: there is no idea to answer yet, and a conversation the operator has not said anything into yet is a normal, valid thing to have sitting on the phone.

agent beats [roles] chatter, which beats [roles] planner - plan::pick run against the same preference order crate::chat::start uses for its own resident conversation. This is a standing chat, not an interview, so chatter rather than planner is the field this conversation is actually about; planner remains the fallback so an operator who never set chatter sees no change. chatter exists at all because this conversation stays open far longer than a single planning interview, and opening it against the same seat as a judge is what produced the agent ... did not answer within 300s timeout that led to splitting the two roles apart - see [roles] chatter’s own doc in crate::config.