fix(playbooks): default pattern_dir to '.' in determine_pattern_dir

Avoid hard failure when -e pattern_dir is omitted; extra-vars still override.
Typical use is running from the pattern repo root.

Co-authored-by: Cursor <cursoragent@cursor.com>

Author: Martin Jackson

playbooks/determine_pattern_dir.yml

@@ -1,17 +1,14 @@
 ---
+# pattern_dir may be overridden with -e pattern_dir=/path/to/pattern (extra vars win over this default).
+# Default '.' is the usual case when ansible-playbook is run from the pattern repository root.
 - name: Determine pattern dir
   hosts: localhost
   connection: local
   gather_facts: false
   become: false
   vars:
-    pattern_dir: ''
+    pattern_dir: '.'
   tasks:
-    - name: Fail if directory is not set
-      ansible.builtin.fail:
-        msg: "pattern_dir variable must be set"
-      when: pattern_dir | length == 0
-
     - name: Set pattern_dir fact for future plays
       ansible.builtin.set_fact:
         pattern_dir: '{{ pattern_dir }}'