refactor(bootstrap,configuration): rename validation-only _normalize.yml files

roles/bootstrap/tasks/_validate.yml

@@ -0,0 +1,11 @@
+---
+# Resolve the OS-specific variable namespace and task file for the bootstrap role.
+- name: Validate OS is supported for bootstrap
+  ansible.builtin.assert:
+    that:
+      - os is defined
+      - os in bootstrap_os_task_map
+    fail_msg: >-
+      Unsupported OS '{{ os | default("undefined") }}' for bootstrap.
+      Supported: {{ bootstrap_os_task_map | dict2items | map(attribute='key') | join(', ') }}
+    quiet: true