Label attached images so agent can understand in-message labels

[charley-oai]

Agent wouldn't "see" attached images and would instead try to use the view_file tool:

In this PR, we wrap image content items in XML tags with the name of each image (now just a numbered name like [Image #1]), so that the model can understand inline image references (based on name). We also put the image content items above the user message which the model seems to prefer (maybe it's more used to definitions being before references).

We also tweak the view_file tool description which seemed to help a bit

Results on a simple eval set of images:

Before

After

[
  {
    "id": "single_describe",
    "prompt": "Describe the attached image in one sentence.",
    "images": ["image_a.png"]
  },
  {
    "id": "single_color",
    "prompt": "What is the dominant color in the image? Answer with a single color word.",
    "images": ["image_b.png"]
  },
  {
    "id": "orientation_check",
    "prompt": "Is the image portrait or landscape? Answer in one sentence.",
    "images": ["image_c.png"]
  },
  {
    "id": "detail_request",
    "prompt": "Look closely at the image and call out any small details you notice.",
    "images": ["image_d.png"]
  },
  {
    "id": "two_images_compare",
    "prompt": "I attached two images. Are they the same or different? Briefly explain.",
    "images": ["image_a.png", "image_b.png"]
  },
  {
    "id": "two_images_captions",
    "prompt": "Provide a short caption for each image (Image 1, Image 2).",
    "images": ["image_c.png", "image_d.png"]
  },
  {
    "id": "multi_image_rank",
    "prompt": "Rank the attached images from most colorful to least colorful.",
    "images": ["image_a.png", "image_b.png", "image_c.png"]
  },
  {
    "id": "multi_image_choice",
    "prompt": "Which image looks more vibrant? Answer with 'Image 1' or 'Image 2'.",
    "images": ["image_b.png", "image_d.png"]
  }
]

Fixes issue #8523

[aibrahim-oai]

Awesome. Code feels cleaner. Let's add integration tests to make sure we send the right request shape to model. We persist the right thing to the rollout file. Maybe a UI snapshot as well.