fix(spark-analytics): escape \\n in JS userPrompt strings

Python triple-quoted string interprets \n as literal newlines,
producing invalid JS string literals and a SyntaxError that
killed the entire script block.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

spark-analytics/base/webview.yaml

@@ -193,11 +193,11 @@ data:
         + 'player behaviour, or game dynamics. When column names reference chess openings (ECO codes, opening names), '
         + 'explain what those openings are.';
 
-      const userPrompt = 'Dataset: "' + dataset.label + '"\n'
-        + 'Total rows: ' + dataset.total_rows + '\n'
-        + 'Columns: ' + dataset.headers.join(', ') + '\n\n'
-        + 'Sample data (first ' + dataset.sample.length + ' rows):\n'
-        + sampleText + '\n\n'
+      const userPrompt = 'Dataset: "' + dataset.label + '"\\n'
+        + 'Total rows: ' + dataset.total_rows + '\\n'
+        + 'Columns: ' + dataset.headers.join(', ') + '\\n\\n'
+        + 'Sample data (first ' + dataset.sample.length + ' rows):\\n'
+        + sampleText + '\\n\\n'
         + 'What does this dataset tell us about chess?';
 
       try {