bootstrap from 2026.9.16.1

The workspace pin names the release the repository bootstraps with. It follows
a release rather than riding in it: 2026.9.16.1 is published, indexed in
openxlings/xim-pkgindex (#845) and mirrored to GitCode with matching digests,
so the pin can move to it now.

Author: speak-agent

.xlings.json

@@ -1,5 +1,5 @@
 {
   "workspace": {
-    "mcpp": "2026.9.15.2"
+    "mcpp": "2026.9.16.1"
   }
 }