feat: setup full Next.js toolchain and core dependencies

- Add runtime deps: react-query, react-hook-form+zod, zustand, ky, openapi-fetch,
  better-auth, react-markdown, shiki, recharts, next-themes, nuqs, sonner, cmdk,
  vaul, embla-carousel-react, motion, date-fns, tailwind-merge, clsx, cva
- Add dev tooling: vitest, testing-library, playwright, prettier(+tailwind plugin),
  husky, lint-staged, jsdom
- Wire providers (QueryClient, Theme, NuqsAdapter, Tooltip, Sonner) into layout
- Add vitest/playwright/prettier configs + lint-staged pre-commit hook
- Add lib/query-client + lib/http (ky) helpers and sample unit test
- Fix react-hooks/set-state-in-effect lint errors (use-mobile useSyncExternalStore,
  carousel async init)
- Remove committed Next-generated types/ duplicates (regenerated under .next/types)

components/ui/message-scroller.tsx

@@ -0,0 +1,130 @@
+"use client";
+
+import * as React from "react";
+import {
+  MessageScroller as MessageScrollerPrimitive,
+  useMessageScroller,
+  useMessageScrollerScrollable,
+  useMessageScrollerVisibility,
+} from "@shadcn/react/message-scroller";
+import { cn } from "cn";
+
+import { Button } from "@/components/ui/button";
+import { ArrowDownIcon } from "lucide-react";
+
+function MessageScrollerProvider(
+  props: React.ComponentProps<typeof MessageScrollerPrimitive.Provider>
+) {
+  return <MessageScrollerPrimitive.Provider {...props} />;
+}
+
+function MessageScroller({
+  className,
+  ...props
+}: React.ComponentProps<typeof MessageScrollerPrimitive.Root>) {
+  return (
+    <MessageScrollerPrimitive.Root
+      data-slot="message-scroller"
+      className={cn(
+        "group/message-scroller relative flex size-full min-h-0 flex-col overflow-hidden",
+        className
+      )}
+      {...props}
+    />
+  );
+}
+
+function MessageScrollerViewport({
+  className,
+  ...props
+}: React.ComponentProps<typeof MessageScrollerPrimitive.Viewport>) {
+  return (
+    <MessageScrollerPrimitive.Viewport
+      data-slot="message-scroller-viewport"
+      className={cn(
+        "size-full min-h-0 min-w-0 scroll-fade-b scrollbar-thin scrollbar-gutter-stable overflow-y-auto overscroll-contain contain-content data-autoscrolling:scrollbar-thumb-transparent data-autoscrolling:scrollbar-track-transparent data-pending-scroll:invisible",
+        className
+      )}
+      {...props}
+    />
+  );
+}
+
+function MessageScrollerContent({
+  className,
+  ...props
+}: React.ComponentProps<typeof MessageScrollerPrimitive.Content>) {
+  return (
+    <MessageScrollerPrimitive.Content
+      data-slot="message-scroller-content"
+      className={cn("flex h-max min-h-full flex-col gap-6", className)}
+      {...props}
+    />
+  );
+}
+
+function MessageScrollerItem({
+  className,
+  scrollAnchor = false,
+  ...props
+}: React.ComponentProps<typeof MessageScrollerPrimitive.Item>) {
+  return (
+    <MessageScrollerPrimitive.Item
+      data-slot="message-scroller-item"
+      scrollAnchor={scrollAnchor}
+      className={cn(
+        "min-w-0 shrink-0 [contain-intrinsic-size:auto_10rem] [content-visibility:auto]",
+        className
+      )}
+      {...props}
+    />
+  );
+}
+
+function MessageScrollerButton({
+  direction = "end",
+  className,
+  children,
+  render,
+  variant = "secondary",
+  size = "icon-sm",
+  ...props
+}: React.ComponentProps<typeof MessageScrollerPrimitive.Button> &
+  Pick<React.ComponentProps<typeof Button>, "variant" | "size">) {
+  return (
+    <MessageScrollerPrimitive.Button
+      data-slot="message-scroller-button"
+      data-direction={direction}
+      data-variant={variant}
+      data-size={size}
+      direction={direction}
+      className={cn(
+        "absolute inset-s-1/2 -translate-x-1/2 border-border bg-background text-foreground transition-[translate,scale,opacity] duration-200 hover:bg-muted hover:text-foreground data-[active=false]:pointer-events-none data-[active=false]:scale-95 data-[active=false]:opacity-0 data-[active=false]:duration-400 data-[active=false]:ease-[cubic-bezier(0.7,0,0.84,0)] data-[active=true]:translate-y-0 data-[active=true]:scale-100 data-[active=true]:opacity-100 data-[active=true]:ease-[cubic-bezier(0.23Line truncated
+        className
+      )}
+      render={render ?? <Button variant={variant} size={size} />}
+      {...props}
+    >
+      {children ?? (
+        <>
+          <ArrowDownIcon />
+          <span className="sr-only">
+            {direction === "end" ? "Scroll to end" : "Scroll to start"}
+          </span>
+        </>
+      )}
+    </MessageScrollerPrimitive.Button>
+  );
+}
+
+export {
+  MessageScrollerProvider,
+  MessageScroller,
+  MessageScrollerViewport,
+  MessageScrollerContent,
+  MessageScrollerItem,
+  MessageScrollerButton,
+  useMessageScroller,
+  useMessageScrollerScrollable,
+  useMessageScrollerVisibility,
+};