Function StripFileUriScheme 

fn StripFileUriScheme(Input: &str) -> &str

Strip a leading file:// (or file:///) scheme from the incoming path. Mirrors the helper in FileSystem.rs; inlined here to avoid a cross-module dependency on a private function in a sibling module. Cocoon sends full URIs like file:///<home>/.land/extensions/... through the legacy openDocument/readFile/stat routes; without stripping, PathBuf roots at the literal scheme string and every read 404s.