[goose-llm] fix image content bug, add optional request_id field

[salman1993]

Changes:

• bugfix: image content processing
• remove logic around detecting image path because goose-llm is remote so that doesn't make sense to try and read images based on path
• add optional request_id that's forwarded to databricks

Error:
The error was in the Databricks provider's image handling code in /src/providers/formats/databricks.rs. Specifically, in the MessageContent::Image handling section:

MessageContent::Image(image) => {
    // Handle direct image content
    content_array.push(json!({
        "type": "image_url",
        "image_url": {
            "url": convert_image(image, image_format)  // ❌ This was the issue
        }
    }));
}

The problem was that convert_image() returns a complete JSON object (not just a URL string), but the code was trying to assign this object to the url field, which should be a string. This caused the API error: "expected a base64-encoded data URL, but got an object instead."

[zhong-sq]

nice! LGTM!