chore: add GPG signing test workflow

Author: maxprilutskiy

.github/workflows/test-gpg.yml

@@ -0,0 +1,47 @@
+name: Test GPG Signing
+
+on:
+  workflow_dispatch:
+
+jobs:
+  test-gpg:
+    runs-on: ubuntu-latest
+    permissions:
+      contents: write
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Import GPG key
+        uses: crazy-max/ghaction-import-gpg@v6
+        with:
+          gpg_private_key: ${{ secrets.GHA_BOT_GPG }}
+          git_user_signingkey: true
+          git_commit_gpgsign: true
+
+      - name: Configure git
+        run: |
+          git config user.name "GitHub Actions"
+          git config user.email "github-actions[bot]@users.noreply.github.com"
+
+      - name: Create test commit
+        run: |
+          echo "test" > test-gpg.txt
+          git add test-gpg.txt
+          git commit -m "test: GPG signing"
+          git log -1 --show-signature
+
+      - name: Verify commit is signed
+        run: |
+          if git log -1 --format="%G?" | grep -q "G"; then
+            echo "✅ Commit is properly signed!"
+          else
+            echo "❌ Commit is NOT signed!"
+            exit 1
+          fi
+
+      - name: Cleanup
+        if: always()
+        run: |
+          git reset --hard HEAD~1
+          rm -f test-gpg.txt