googleThinkingLevelFor function
Maps our thinking ladder rung onto Gemini's ThinkingLevel enum
values; unknown rungs (none today after the clamp) map to null.
Implementation
String? googleThinkingLevelFor(String? level) => switch (level) {
'minimal' => 'MINIMAL',
'low' => 'LOW',
'medium' => 'MEDIUM',
'high' => 'HIGH',
_ => null,
};