Refine the store assistant UI and gate it behind a flag

- Gate the assistant on NEXT_PUBLIC_ENABLE_AI=1 (UI only; the /api/chat
  route still responds if called directly)
- Chat model is openai/gpt-5.6-luna-pro with reasoning requested and
  sendReasoning enabled, rendered via the Reasoning component
- Suggestion chips and reasoning come from ai-elements; attachments gain
  hover-card previews, left alignment, and render under the user message
- Launcher: plain Button when closed, magicui RainbowButton when open
- Tool results replace the collapsible Tool UI with a shimmer while
  running and a muted icon + summary line after, plus product previews
- Commerce icons in place of the folder icon for collections
- Add a thin announcement bar above the header; footer splits links and
  socials onto separate rows and clears the launcher corner
- Add the shadcn base layer so Tailwind v4's bare `border` picks up the
  theme colour instead of currentColor

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016jWbNNJLksC1QG8z8845FX

components/ai-elements/suggestion.tsx

@@ -0,0 +1,57 @@
+"use client";
+
+import { Button } from "@/components/ui/button";
+import {
+  ScrollArea,
+  ScrollBar,
+} from "@/components/ui/scroll-area";
+import { cn } from "@/lib/utils";
+import type { ComponentProps } from "react";
+import { useCallback } from "react";
+
+export type SuggestionsProps = ComponentProps<typeof ScrollArea>;
+
+export const Suggestions = ({
+  className,
+  children,
+  ...props
+}: SuggestionsProps) => (
+  <ScrollArea className="w-full overflow-x-auto whitespace-nowrap" {...props}>
+    <div className={cn("flex w-max flex-nowrap items-center gap-2", className)}>
+      {children}
+    </div>
+    <ScrollBar className="hidden" orientation="horizontal" />
+  </ScrollArea>
+);
+
+export type SuggestionProps = Omit<ComponentProps<typeof Button>, "onClick"> & {
+  suggestion: string;
+  onClick?: (suggestion: string) => void;
+};
+
+export const Suggestion = ({
+  suggestion,
+  onClick,
+  className,
+  variant = "outline",
+  size = "sm",
+  children,
+  ...props
+}: SuggestionProps) => {
+  const handleClick = useCallback(() => {
+    onClick?.(suggestion);
+  }, [onClick, suggestion]);
+
+  return (
+    <Button
+      className={cn("cursor-pointer rounded-full px-4", className)}
+      onClick={handleClick}
+      size={size}
+      type="button"
+      variant={variant}
+      {...props}
+    >
+      {children || suggestion}
+    </Button>
+  );
+};