fix: use sandbox mime_type input field

Author: malsabbagh05

src/google/adk/code_executors/agent_engine_sandbox_code_executor.py

@@ -181,7 +181,7 @@ def execute_code(
           {
               'name': f.name,
               'content': f.content,
-              'mimeType': f.mime_type,
+              'mime_type': f.mime_type,
           }
           for f in code_execution_input.input_files
       ]

tests/unittests/code_executors/test_agent_engine_sandbox_code_executor.py

@@ -127,12 +127,12 @@ def test_execute_code_success(
     )
 
   @patch("vertexai.Client")
-  def test_execute_code_sends_input_files_with_content_key(
+  def test_execute_code_sends_input_files_with_sandbox_api_fields(
       self,
       mock_vertexai_client,
       mock_invocation_context,
   ):
-    """Input files must be sent under the 'content' key the SDK expects."""
+    """Input files must use the field names the sandbox API expects."""
     mock_api_client = MagicMock()
     mock_vertexai_client.return_value = mock_api_client
     mock_response = MagicMock()
@@ -157,7 +157,7 @@ def test_execute_code_sends_input_files_with_content_key(
     )
     sent_files = call_kwargs["input_data"]["files"]
     assert sent_files == [
-        {"name": "data.csv", "content": "a,b,c", "mimeType": "text/csv"}
+        {"name": "data.csv", "content": "a,b,c", "mime_type": "text/csv"}
     ]
 
   @patch("vertexai.Client")