fix Gemini structured output for 3 series models and adapt schema

Author: ilvalerione

src/Providers/Gemini/HandleStructured.php

@@ -13,17 +13,17 @@
 use function json_encode;
 use function in_array;
 
-/**
- * Structured outputs with tools is available only for the Gemini 3 series models.
- * https://ai.google.dev/gemini-api/docs/structured-output?example=recipe#structured_outputs_with_tools
- */
-const SUPPORTED_MODELS = [
-    'gemini-3-pro-preview',
-    'gemini-3-flash-preview',
-];
-
 trait HandleStructured
 {
+    /**
+     * Structured outputs with tools is available only for the Gemini 3 series models.
+     * https://ai.google.dev/gemini-api/docs/structured-output?example=recipe#structured_outputs_with_tools
+     */
+    protected array $supportedModels = [
+        'gemini-3-pro-preview',
+        'gemini-3-flash-preview',
+    ];
+
     public function structured(
         array $messages,
         string $class,
@@ -37,7 +37,7 @@ public function structured(
 
         // Gemini does not support structured output in combination with tools.
         // So we try to work with a JSON mode in case the agent has some tools defined.
-        if (!empty($this->tools) && !in_array($this->model, SUPPORTED_MODELS)) {
+        if (!empty($this->tools) && !in_array($this->model, $this->supportedModels)) {
             $last_message = end($messages);
             if ($last_message instanceof Message && $last_message->getRole() === MessageRole::USER->value) {
                 $last_message->setContent(