Function open_outer_session 

pub fn open_outer_session(
    configured: &ConfiguredWarmStartStore,
    key: &str,
) -> Option<Arc<Session>>

Open a gam_runtime::warm_start::Session for outer-iterate (rho-axis) checkpoints.

Uses a different fingerprint tag than the inner warm-start-key absorption (see load_json_record) so the outer-iterate keyspace is disjoint from the inner beta-record keyspace — the two layers persist different payload shapes and must not alias.