fix: use netlify --json for URL capture; soften no-RST-files note

Agent-Logs-Url: https://github.com/nextcloud/documentation/sessions/b0dedceb-7f42-453c-9ddf-a0d130183f1d

Co-authored-by: skjnldsv <14975046+skjnldsv@users.noreply.github.com>

Author: Copilot

.github/workflows/sphinxbuild.yml

@@ -634,15 +634,16 @@ jobs:
         continue-on-error: true
         run: |
           set +e
-          output=$(netlify deploy \
+          json=$(netlify deploy \
             --dir=netlify-deploy \
             --site="${{ secrets.NETLIFY_SITE_ID }}" \
             --auth="${{ secrets.NETLIFY_AUTH_TOKEN }}" \
             --alias="pr-${{ github.event.pull_request.number }}" \
-            --message="Preview for PR #${{ github.event.pull_request.number }}" 2>&1)
+            --message="Preview for PR #${{ github.event.pull_request.number }}" \
+            --json 2>/dev/null)
           exit_code=$?
-          echo "$output"
-          preview_url=$(echo "$output" | grep -oP 'Website URL:\s+\K\S+' | head -1)
+          echo "$json"
+          preview_url=$(echo "$json" | jq -r '.deploy_url // .url // ""' 2>/dev/null || echo "")
           echo "url=${preview_url}" >> "$GITHUB_OUTPUT"
           exit $exit_code
 
@@ -693,7 +694,7 @@ jobs:
                 '</details>',
               ].join('\n');
             } else if (rstFiles.length === 0) {
-              changedSection = '\n_No RST documentation files changed._';
+              changedSection = '\n_No RST documentation pages changed in this PR._';
             }
 
             // Compose the full comment body