Add gh-aw agentic workflow for upgrading Python libraries (#7117)

* Add gh-aw agentic workflow for upgrading Python libraries

- upgrade-pylib.md: Claude-based workflow triggered via workflow_dispatch
- Runs `scripts/update_lib quick <name>` to sync a library from CPython
- Creates a PR with the result, referencing issue #6839

.gitattributes

@@ -66,3 +66,5 @@ Lib/test/certdata/*.0                               generated
 Lib/test/levenshtein_examples.json                  generated
 Lib/test/test_stable_abi_ctypes.py                  generated
 Lib/token.py                                        generated
+
+.github/workflows/*.lock.yml linguist-generated=true merge=ours