Support for an file upload component (image upload, PDF upload etc)

[jacobsimionato]

It would be handy for some use cases to have a component that represents a file upload slot. Some thoughts:

• The contract could specify how the file is sent via A2A, which already has a FilePart etc
• The client would ideally show the uploaded file name and progress in the UI
• The UI would be flexible and look different on different devices e.g. a drop zone on web, or a button to open a picker on mobile
• There should be type filtering, to allow for specifically an image picker etc. Perhaps this is a usageHint.
• On mobile, it must be possible to make this an image picker which opens the phone gallery/camera

[crispysocks]

To some extent, the current text-based interaction model already supports file uploads; A2UI should address how an LLM can present and interact with information for us.

Perhaps a different approach would help: could A2UIs let the LLM proactively render UI components and load local file data for layout?