fix: auto-tag checkout に fetch-depth: 0 を追加（PR head SHA が shallow clone に存在しない問題）

.github/workflows/auto-tag.yml

@@ -18,6 +18,8 @@ jobs:
       tag: ${{ steps.version.outputs.tag }}
     steps:
       - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
 
       - name: Extract version from PR title
         id: version