refactor(environment): split main.yml into focused sub-task files

roles/environment/tasks/_thirdparty.yml

@@ -0,0 +1,27 @@
+---
+- name: Check for third-party preparation tasks
+  run_once: true
+  become: false
+  delegate_to: localhost
+  vars:
+    ansible_connection: local
+  block:
+    - name: Resolve third-party preparation task path
+      ansible.builtin.set_fact:
+        environment_thirdparty_tasks_path: >-
+          {{
+            thirdparty_tasks
+            if thirdparty_tasks | regex_search('^/')
+            else playbook_dir + '/' + thirdparty_tasks
+          }}
+
+    - name: Stat third-party preparation tasks
+      ansible.builtin.stat:
+        path: "{{ environment_thirdparty_tasks_path }}"
+      register: environment_thirdparty_tasks_stat
+
+- name: Run third-party preparation tasks
+  when:
+    - thirdparty_tasks | length > 0
+    - environment_thirdparty_tasks_stat.stat.exists
+  ansible.builtin.include_tasks: "{{ environment_thirdparty_tasks_path }}"