Address Copilot review: gate auto-merge on patch/minor only

- Use PR author check instead of github.actor for reliability
- Add dependabot/fetch-metadata to gate on semver patch/minor
- Use GH_TOKEN instead of GITHUB_TOKEN for gh CLI consistency

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: ksroda-sa

.github/workflows/dependabot-auto-merge.yml

@@ -9,15 +9,22 @@ permissions:
 jobs:
   auto-merge:
     runs-on: ubuntu-latest
-    if: github.actor == 'dependabot[bot]'
+    if: github.event.pull_request.user.login == 'dependabot[bot]'
     steps:
+      - name: Fetch Dependabot metadata
+        id: metadata
+        uses: dependabot/fetch-metadata@v2
+        with:
+          github-token: ${{ secrets.GITHUB_TOKEN }}
       - name: Approve PR
+        if: steps.metadata.outputs.update-type == 'version-update:semver-patch' || steps.metadata.outputs.update-type == 'version-update:semver-minor'
         run: gh pr review --approve "$PR_URL"
         env:
           PR_URL: ${{ github.event.pull_request.html_url }}
-          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
       - name: Enable auto-merge
+        if: steps.metadata.outputs.update-type == 'version-update:semver-patch' || steps.metadata.outputs.update-type == 'version-update:semver-minor'
         run: gh pr merge --auto --squash "$PR_URL"
         env:
           PR_URL: ${{ github.event.pull_request.html_url }}
-          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}