Function lashlang_durability_tier 

pub fn lashlang_durability_tier(tier: DurabilityTier) -> DurabilityTier

Map the lashlang language crate’s durability tier onto the runtime’s lash_core::DurabilityTier. The two enums are parallel; this is the single bridge point between them (the parallel LashlangDurabilityTier alias is gone — process engines self-describe their tier via lash_core::DurabilityTier).