Function plan_install 

pub fn plan_install(
    ecosystem: &Ecosystem,
    profile: &GameProfile,
    package_full_name: &str,
    extracted_root: &Path,
    archive_path: Option<&Path>,
) -> Result<InstallPlan>

Builds an InstallPlan for a package.

If package_full_name is in the ecosystem’s mod-loader registry, the package is a loader pack and unpacks to the root; otherwise its files are routed by the profile’s InstallRules. archive_path is the package’s original zip, needed only for package-zip loaders (e.g. GodotML); pass None when unavailable.