chore(ci): add release/** to checks workflow trigger

The Checks workflow only triggered on PRs targeting main. PRs targeting
release branches (e.g. release-please PRs) never got the required
Validate PR title and ci checks, blocking merge.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Signed-off-by: Mary Dickson <mary.dickson@virtru.com>

Author: marythought

.github/workflows/checks.yaml

@@ -4,6 +4,7 @@ on:
   pull_request:
     branches:
       - main
+      - 'release/**'
   push:
     branches:
       - main