feat(webui): render ask_user choices

Made-with: Cursor

webui/src/lib/types.ts

@@ -44,6 +44,8 @@ export interface UIMessage {
   images?: UIImage[];
   /** Signed or local UI-renderable media attachments. */
   media?: UIMediaAttachment[];
+  /** Optional answer choices for a pending ask_user question. */
+  buttons?: string[][];
 }
 
 export interface ChatSummary {
@@ -82,6 +84,9 @@ export type InboundEvent =
       reply_to?: string;
       media?: string[];
       media_urls?: Array<{ url: string; name?: string }>;
+      buttons?: string[][];
+      /** Original prompt before the websocket text fallback appends buttons. */
+      button_prompt?: string;
       /** Present when the frame is an agent breadcrumb (e.g. tool hint,
        * generic progress line) rather than a conversational reply. */
       kind?: "tool_hint" | "progress";