Add canonical overview vignette entry point

Author: OVVO-Financial

examples/vignettes/01_overview.py

@@ -0,0 +1,12 @@
+"""Canonical vignette 01: Overview.
+
+Source of truth:
+    NNS/vignettes/NNSvignette_01_Overview.Rmd
+
+The maintained implementation lives in ``overview.py``. This numbered entry
+point keeps the Python example catalog aligned with the canonical R sequence.
+"""
+from overview import main
+
+if __name__ == "__main__":
+    main()