Lets you click Undo under a user message to drop it and everything
after it, refilling the prompt with that message's text/images so it
can be edited and resent.
Paste images into the textarea to attach them to a message. Pending
images show as thumbnails above the input with a × remove button.
Images are sent to all three providers (OpenAI image_url, Anthropic
image_url via compat endpoint, Gemini inline_data).
abdus