fix(ci): prune duplicate github-pages artifacts before deploy

upload-pages-artifact@v3 occasionally uploads the same artifact multiple
times in a single run on transient network hiccups, which then makes
deploy-pages@v4 fail with 'Multiple artifacts named github-pages'.
Prune step keeps the newest, deletes the rest.

Author: hqhq1025

.github/workflows/deploy-website.yml

@@ -50,7 +50,37 @@ jobs:
       url: ${{ steps.deployment.outputs.page_url }}
     needs: build
     runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      pages: write
+      id-token: write
+      actions: write
     steps:
+      # Work around actions/upload-pages-artifact@v3 bug where transient
+      # network hiccups during upload can produce >1 artifact named
+      # "github-pages" in a single run, which then makes deploy-pages@v4
+      # fail with "Multiple artifacts named 'github-pages'". Delete all
+      # but the most recent before deploying.
+      - name: Prune duplicate github-pages artifacts
+        env:
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          RUN_ID: ${{ github.run_id }}
+          REPO: ${{ github.repository }}
+        run: |
+          set -euo pipefail
+          artifacts=$(gh api "/repos/$REPO/actions/runs/$RUN_ID/artifacts" \
+            --jq '[.artifacts[] | select(.name == "github-pages")] | sort_by(.created_at) | reverse')
+          count=$(echo "$artifacts" | jq 'length')
+          echo "Found $count github-pages artifact(s) in this run."
+          if [ "$count" -le 1 ]; then
+            exit 0
+          fi
+          # Keep index 0 (newest); delete the rest.
+          echo "$artifacts" | jq -r '.[1:] | .[].id' | while read -r id; do
+            echo "Deleting duplicate artifact $id"
+            gh api -X DELETE "/repos/$REPO/actions/artifacts/$id"
+          done
+
       - name: Deploy to GitHub Pages
         id: deployment
         uses: actions/deploy-pages@v4