fix(ci): grant pull-requests write permission to release workflow (#388)

changesets/action이 "chore: version packages" 릴리즈 PR을 생성하려면
pull-requests: write 권한이 필요한데, permissions 블록에 id-token과 contents만
지정되어 있어 PR 생성 단계에서 "Resource not accessible by integration"으로
실패하고 있었습니다.

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: okinawaa

.github/workflows/release.yml

@@ -11,6 +11,7 @@ jobs:
     permissions:
       id-token: write
       contents: write
+      pull-requests: write
     steps:
       - name: Checkout Repository
         uses: actions/checkout@v5