feat: datetime reports, auto-commit on verify, register pruning EP

- Include time in TAP report filename (ISO 8601: date + HHmmssZ)
- Add changed_when: false to report write task — verify play now shows
  changed=0 on a clean run (all green recap)
- make verify auto-commits new reports to repo after a passing run;
  exits non-zero before committing if assertions fail
- Register EP-RAIL-001: report pruning extension point for future
  implementation when reports/ accumulates beyond a threshold

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

ansible/roles/goss/tasks/main.yml

@@ -50,7 +50,8 @@
 - name: Write TAP report locally
   ansible.builtin.copy:
     content: "{{ goss_result.stdout }}"
-    dest: "{{ playbook_dir }}/../../reports/goss-{{ inventory_hostname }}-{{ ansible_date_time.date }}.tap"
+    dest: "{{ playbook_dir }}/../../reports/goss-{{ inventory_hostname }}-{{ ansible_date_time.date }}T{{ ansible_date_time.hour }}{{ ansible_date_time.minute }}{{ ansible_date_time.second }}Z.tap"
     mode: "0644"
   delegate_to: localhost
   become: false
+  changed_when: false