Function resolve_env 

pub fn resolve_env(
    default_env: &BTreeMap<String, String>,
    cfg: &RepoProviderConfig,
    process_env: &dyn Fn(&str) -> Option<String>,
) -> BTreeMap<String, String>

Resolve the environment overlay for a repo’s caliband daemon.

Layered lowest → highest: default_env (global) → curated provider fields → cfg.env (raw). process_env looks up prosperod’s own environment for api_key_from_env references.