Restored reliable Gemini file uploads

We resolved a 400 error caused by message formatting for file Part objects in Gemini (Vertex AI) uploads. Uploads now work as expected, unblocking multimodal use cases.

Details:

• No action required; existing integrations resume normal behavior
• Applies to Gemini file inputs via Vertex AI

Who this is for: Teams relying on Gemini for multimodal processing and document-aware workflows.