extract static method
Extracts the first JSON object or array from text.
Handles fenced blocks (```json or ```), leading and
trailing prose, and nested braces inside strings. Returns null when no
valid JSON is present.
Implementation
static Object? extract(String text) {
for (final candidate in _candidates(text)) {
final decoded = _tryDecode(candidate);
if (decoded != null) return decoded;
}
return null;
}