Fix bash path for NixOS in ringtail playbook

NixOS doesn't have /bin/bash. Use /run/current-system/sw/bin/bash
which is the stable PATH-resolved location on NixOS.

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

ansible/playbooks/ringtail.yml

@@ -99,7 +99,7 @@
             --namespace=1password \
             --from-literal=1password-credentials.json='{{ _op_credentials.stdout }}' \
             --dry-run=client -o yaml | k3s kubectl apply -f -
-        executable: /bin/bash
+        executable: /run/current-system/sw/bin/bash
       changed_when: true
       no_log: true
 
@@ -111,6 +111,6 @@
             --namespace=1password \
             --from-literal=token={{ _op_token.stdout }} \
             --dry-run=client -o yaml | k3s kubectl apply -f -
-        executable: /bin/bash
+        executable: /run/current-system/sw/bin/bash
       changed_when: true
       no_log: true