ci: harden workflow dedup and badge gating

.gitea/workflows/pr-validation.yml

@@ -153,11 +153,24 @@ jobs:
           cache: true
           cache-dependency-path: go.sum
 
+      - name: Check coverage artefacts
+        id: coverage-files
+        if: ${{ always() && steps.coverage.outcome == 'success' }}
+        run: |
+          set -euo pipefail
+          if [[ -f coverage.out ]]; then
+            echo "exists=true" >> "$GITHUB_OUTPUT"
+          else
+            echo "exists=false" >> "$GITHUB_OUTPUT"
+            echo "coverage.out was not produced; skipping coverage badge upload." >> "$GITHUB_STEP_SUMMARY"
+          fi
+
       - name: Upload coverage badge
         id: badge
-        if: ${{ always() && steps.coverage.outcome == 'success' }}
+        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 }}
 
@@ -178,6 +191,7 @@ jobs:
       - name: Decorate PR
         if: ${{ always() }}
         uses: https://git.hrafn.xyz/aether/vociferate/decorate-pr@v1.1.0
+        continue-on-error: true
         with:
           coverage-percentage: ${{ steps.badge.outputs.total }}
           badge-url: ${{ steps.badge.outputs.badge-url }}