chore(ci): fix Mergify deprecation — move queue.method to queue_rules.merge_method (#36)

Mergify flagged on the rollout PR (#32): the
\`pull_request_rules → actions → queue → method\` field is deprecated.
Mergify v2 wants \`merge_method:\` on the queue_rule itself.

Co-authored-by: Gk <gk@Gks-MacBook-Pro.local>
Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: 3 people

.mergify.yml

@@ -10,6 +10,9 @@
 
 queue_rules:
   - name: dependencies
+    # ``merge_method`` lives on the queue rule (Mergify v2). The deprecated
+    # ``method:`` field on ``actions.queue`` was removed.
+    merge_method: squash
     batch_size: 5
     batch_max_wait_time: 30 m
     merge_conditions:
@@ -30,4 +33,3 @@ pull_request_rules:
     actions:
       queue:
         name: dependencies
-        method: squash