Function resolve_file_or_session 

pub fn resolve_file_or_session(
    file: PathBuf,
    session: Option<String>,
    workspace: Option<PathBuf>,
) -> Result<(PathBuf, Option<NamedTempFile>)>

Resolve the effective workbook path, optionally materializing from a session.

When session is Some, the session’s current state is materialized to a temp file whose path is returned. The caller must keep the returned NamedTempFile alive for the duration of the read operation.

When session is None, the provided file path is returned as-is.