Function is_api_embed_backend 

pub fn is_api_embed_backend(backend: &str) -> bool

#1598 — true when the embedding backend speaks an API wire shape (OpenAI-compatible /embeddings + Bearer auth) rather than the local Ollama-native /api/embed shape. "ollama" is the ONLY non-API backend; every #1067 alias and the generic openai-compatible escape hatch classify as API backends. Sits next to [alias_api_key_env_vars_for_resolver] / [backend_default_base_url] — the alias machinery it complements.