[wip] Rework load_libraryfile and LazyLibrary using overlays

masque/library.py

@@ -131,6 +131,15 @@ class ILibraryView(Mapping[str, 'Pattern'], metaclass=ABCMeta):
         """
         return Abstract(name=name, ports=self[name].ports)
 
+    def source_order(self) -> tuple[str, ...]:
+        """
+        Return names in the library's preferred source order.
+
+        Source-backed views may override this to preserve on-disk ordering
+        without materializing patterns.
+        """
+        return tuple(self.keys())
+
     def dangling_refs(
             self,
             tops: str | Sequence[str] | None = None,