Add a Sketch & Annotation Whiteboard Tool for Agent-User Collaboration

[iwangbowen]

Would it make sense to add a lightweight WebView-based whiteboard to Seamless Agent? The idea: agents could proactively open it when visual context helps, and users could open it manually during askUser prompts to annotate images or draw sketches — with the results returned as attachments the agent can consume.

The tool would support multiple canvases per session, image import with freehand annotation (markup, labels, highlights), and blank-canvas sketching for wireframes or diagrams. All canvases could be submitted together as a single structured response.