Function is_gdn_key 

pub fn is_gdn_key(key: &str) -> bool

Whether key names a GDN / linear-attention tensor — the family classify_key rejects outright.

Exists so a caller can SKIP such a tensor under ATLAS_LORA_ALLOW_PARTIAL instead of pattern-matching on the reject message. The prefix test is the same one classify_key uses; keep them together so the skip can never drift from the reject.