The image-strip fallback (triggered when a model errors on image input)
replaced image_url blocks with [image: <path>] or [image omitted]. Both
read like a live, available image to the LLM, causing it to:
1. hallucinate about image contents it never received
2. attempt read_file on the leaked server path
3. expose internal file paths to the model
Replace with an explicit '[Image not delivered to model — do not describe
or reference it]' placeholder that tells the LLM the image was stripped.
Fixes#4345
Xubin Ren
michaelxerandXubin Ren