Unify host and native filesystem acquisition

docs/roadmap/implementation.md

@@ -282,6 +282,16 @@ growth avoids accumulated full-tree copying. Run the everyday checker and
 
 ## Stage 3: Unify private filesystem acquisition without public changes
 
+**Completed 2026-09-29.** Imports, glob traversal, and selected-overlay loading
+now use a private access boundary with the existing contained host backend and
+a native `fs.FS` backend. Namespace tokens and occurrence identities are separate
+from labels and paths; repetition tracking is composition-local and input/glob
+accounting can be shared. Native tests cover slash-relative imports, sorted
+globs, optional missing paths, root escape, overlays, repeated/cyclic imports,
+non-comparable filesystems, and handle closure on success and representative
+failures. Existing host tests, focused native tests, and the everyday checker
+passed. No public constructor or context field was added.
+
 Scope: engine source/file, filesystem, import, glob, and selected-overlay code.
 
 1. Extract a small private namespace/access boundary used by imports and overlays.