ci: remove fragile external badge actions

.gitea/workflows/pr-validation.yml

@@ -168,11 +168,15 @@ jobs:
       - name: Upload coverage badge
         id: badge
         if: ${{ always() && steps.coverage.outcome == 'success' && steps.coverage-files.outputs.exists == 'true' }}
-        uses: https://git.hrafn.xyz/aether/vociferate/coverage-badge@v1.1.0
-        with:
-          coverage-profile: coverage.out
-          artefact-bucket-name: ${{ vars.ARTEFACT_BUCKET_NAME }}
-          artefact-bucket-endpoint: ${{ vars.ARTEFACT_BUCKET_ENDPONT }}
+        run: |
+          set -euo pipefail
+          total="$(go tool cover -func=coverage.out | awk '/^total:/ {sub(/%/, "", $3); print $3}')"
+          if [[ -z "$total" ]]; then
+            total="n/a"
+          fi
+          echo "total=${total}" >> "$GITHUB_OUTPUT"
+          echo "report-url=n/a" >> "$GITHUB_OUTPUT"
+          echo "badge-url=n/a" >> "$GITHUB_OUTPUT"
 
       - name: Validate changelog gate
         if: ${{ always() }}