Function is_standard_decisions_endpoint 

pub fn is_standard_decisions_endpoint(base_url: &str) -> bool

Whether base_url is the direct standard OpenAI endpoint Decisions requires.

Shared by the runtime OpenAIProvider::decisions_eligible gate and the /model picker’s non-I/O eligibility mirror, so the two cannot drift. Empty input is not standard: callers that treat “no override” as eligible must filter empties before calling this.