fix(dev_tools): display JSON columns with brackets in SQL query tool

JSON arrays like [11, 4, 10] were rendered as "11,4,10" because
String() on a JS array drops brackets. Now uses JSON.stringify()
for object/array values.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

app/modules/dev_tools/static/admin/js/sql-query.js

@@ -454,6 +454,7 @@ function sqlQueryTool() {
 
         formatCell(val) {
             if (val === null || val === undefined) return 'NULL';
+            if (typeof val === 'object') return JSON.stringify(val);
             return String(val);
         },