Fix TypeError in AssistantMessageNormalizer when toolCalls is null

Author: Muneer-Shafi

src/platform/tests/Bridge/Anthropic/Contract/AssistantMessageNormalizerTest.php

@@ -55,11 +55,22 @@ public function testNormalize(AssistantMessage $message, array $expectedOutput)
 
         $normalized = $normalizer->normalize($message);
 
-        $this->assertEquals($expectedOutput, $normalized);
+        $this->assertSame($expectedOutput, $normalized);
     }
 
     /**
-     * @return iterable<string, array{AssistantMessage, array{text?: string, functionCall?: array{id: string, name: string, args?: mixed}}[]}>
+     * @return iterable<string, array{
+     *     0: AssistantMessage,
+     *     1: array{
+     *         role: 'assistant',
+     *         content: string|list<array{
+     *             type: 'tool_use',
+     *             id: string,
+     *             name: string,
+     *             input: array<string, mixed>|\stdClass
+     *         }>
+     *     }
+     * }>
      */
     public static function normalizeDataProvider(): iterable
     {