Function discover_compatibility_paths 

pub fn discover_compatibility_paths(
    home_dir: Option<&Path>,
    cli_overrides: &PathOverrides,
    env_map: &HashMap<String, String, impl BuildHasher>,
    file_config: &CompatibilityConfig,
) -> Result<CompatibilityPaths, CompatibilityError>

Resolve effective compatibility paths with strict precedence: CLI flag overrides -> environment variables -> config file -> defaults.