Function build_turn_argv 

pub(super) fn build_turn_argv(
    base: &[String],
    resume_strategy: &str,
    resume_flag: &str,
    session_id: Option<&str>,
) -> Result<Vec<String>, String>

Build the argv for one provider turn, adding session continuation when a prior session id is available.

Existing providers use a trailing flag (--resume <id> / -r <id>). Codex is different: its continuation command is codex exec resume [OPTIONS] <id> -, so resume must be inserted after exec and the session id must remain before the stdin prompt marker.