Function decode_rollback_ring_slots_with 

pub fn decode_rollback_ring_slots_with(
    num_ssm_layers: usize,
    use_speculative: bool,
    published: Option<usize>,
    ring_override: Option<&str>,
    watchdogs_disabled: bool,
) -> DecodeRingDecision

2026-09-25: Env-free core of decode_rollback_ring_slots. Precedence, highest first:

1. no SSM layers: 0;
2. published: that depth, also under speculative decode or with watchdogs disabled;
3. ring_override "1" or "0": DECODE_ROLLBACK_RING_SLOTS or 0;
4. speculative decode or watchdogs disabled: 0, with a skip_reason;
5. otherwise DECODE_ROLLBACK_RING_SLOTS.