Function resolve_gqa_pack 

pub fn resolve_gqa_pack(declared: bool, env_raw: Option<&str>) -> bool

DECODE_GQA_PACK_DECLARED, overridden by AVAROK_ATTN_DECODE_GQA_PACK.

Pure in its arguments so the resolution is testable without touching the process environment; gqa_pack_enabled is the one site that reads it.