Function persisted_login 

pub fn persisted_login(
    channel: QrPairingChannel,
    config: &Config,
    alias: &str,
) -> PersistedLogin

Probe the persisted login state for a channel alias.

Callers resolve their channel type key to QrPairingChannel once via crate::listing::qr_pairing_channel and dispatch on the typed value; no string key reaches this function. The match below is exhaustive over the feature-gated variant set, so adding a QR-pairing channel without a probe arm is a compile error rather than a silent fallthrough.