Generate dynamic diagrams (via Excalidraw) (#940)

Add support for generating dynamic diagrams in flow with Excalidraw (https://github.com/excalidraw/excalidraw). This happens in three steps:
1. Default information collection & intent determination step.
2. Improving the overall guidance of the prompt for generating a JSON, Excalidraw-compatible declaration.
3. Generation of the diagram to output to the final UI.

Add support in the web UI.

src/interface/web/app/common/iconUtils.tsx

@@ -48,6 +48,7 @@ import {
     Oven,
     Gavel,
     Broadcast,
+    KeyReturn,
 } from "@phosphor-icons/react";
 import { Markdown, OrgMode, Pdf, Word } from "@/app/components/logo/fileLogo";
 
@@ -193,6 +194,10 @@ export function getIconForSlashCommand(command: string, customClassName: string
     }
 
     if (command.includes("default")) {
+        return <KeyReturn className={className} />;
+    }
+
+    if (command.includes("diagram")) {
         return <Shapes className={className} />;
     }