infra: build api docs from package listing (#27774)

.github/scripts/check_diff.py

@@ -300,6 +300,8 @@ if __name__ == "__main__":
             ] != ["README.md"]:
                 dirs_to_run["test"].add(f"libs/partners/{partner_dir}")
             # Skip if the directory was deleted or is just a tombstone readme
+        elif file == "libs/packages.yml":
+            continue
         elif file.startswith("libs/"):
             raise ValueError(
                 f"Unknown lib: {file}. check_diff.py likely needs "