chore: use platform arch as digest

Signed-off-by: JohnsonRan <me@ihtw.moe>

.github/workflows/docker-image.yml

@@ -34,6 +34,10 @@ jobs:
     runs-on: ${{ matrix.os }}
 
     steps:
+      - name: Prepare platform name
+        run: |
+          echo "PLATFORM_NAME=${{ matrix.platform }}" | sed 's|/|-|g' >> $GITHUB_ENV
+
       - name: Checkout source code
         uses: actions/checkout@v4
 
@@ -79,7 +83,7 @@ jobs:
       - name: Upload digest
         uses: actions/upload-artifact@v4
         with:
-          name: digests-${{ strategy.job-index }}
+          name: digests-${{ env.PLATFORM_NAME }}
           path: /tmp/digests/*
           if-no-files-found: error
           retention-days: 1