refactor: introduce write_todos tool for enhanced task management

- Added a new write_todos tool to facilitate the creation and management of planning lists within the chat interface.
- Updated system prompt with detailed instructions on using the write_todos tool, including usage patterns and restrictions.
- Enhanced the chat message handling to support the new tool, ensuring proper integration and user experience.
- Implemented UI components for displaying and interacting with the planning lists, including progress tracking and status indicators.

surfsense_web/components/tool-ui/plan/index.tsx

@@ -0,0 +1,53 @@
+"use client";
+
+import { Component, type ReactNode } from "react";
+import { Card, CardContent } from "@/components/ui/card";
+
+export * from "./plan";
+export * from "./schema";
+
+// ============================================================================
+// Error Boundary
+// ============================================================================
+
+interface PlanErrorBoundaryProps {
+  children: ReactNode;
+  fallback?: ReactNode;
+}
+
+interface PlanErrorBoundaryState {
+  hasError: boolean;
+  error?: Error;
+}
+
+export class PlanErrorBoundary extends Component<PlanErrorBoundaryProps, PlanErrorBoundaryState> {
+  constructor(props: PlanErrorBoundaryProps) {
+    super(props);
+    this.state = { hasError: false };
+  }
+
+  static getDerivedStateFromError(error: Error): PlanErrorBoundaryState {
+    return { hasError: true, error };
+  }
+
+  render() {
+    if (this.state.hasError) {
+      if (this.props.fallback) {
+        return this.props.fallback;
+      }
+
+      return (
+        <Card className="w-full max-w-xl border-destructive/50">
+          <CardContent className="pt-6">
+            <div className="flex items-center gap-2 text-destructive">
+              <span className="text-sm">Failed to render plan</span>
+            </div>
+          </CardContent>
+        </Card>
+      );
+    }
+
+    return this.props.children;
+  }
+}
+