Function load_layered_config 

pub fn load_layered_config(
    cwd: Option<&Path>,
    flags: &SessionFlags,
) -> Result<LayeredLoad>

Load the full layered configuration: defaults < user file < project file < session flags. cwd locates the project layer (<git-root>/.mermaid/config.toml, sanitized + safety-clamped); pass None to skip it (daemon, tests).