Function run_bridge 

pub async fn run_bridge(
    app_token: String,
    bot_token: String,
    channel_id: String,
    target_agent: Option<String>,
    http: Client,
    outbound_rx: UnboundedReceiver<OutboundMsg>,
    health: Arc<Mutex<BridgeHealth>>,
)

Orchestrates the two independent tasks described in the module doc comment. Called once from SlackBridge::init_global’s spawned task.