fix(cf): lazy-load MarkdownChat to shrink worker bundle further

MarkdownChat statically imports remark-math, remark-gfm, remark-directive,
rehype-katex, rehype-highlight, plus side-effect CSS for katex and
highlight.js, and renders MermaidBlock/FunctionPlot. Even though the
component is "use client", static-importing it from ChatPanel.tsx,
screens/Library.tsx, and screens/Study.tsx pulled the whole markdown
stack into the OpenNext server handler.

Switch all three call sites to `dynamic(() => import(...), { ssr: false })`
so MarkdownChat becomes a separate client chunk.

Local cf:build verification:
  - handler.mjs uncompressed: 9,933 KiB → 5,041 KiB
  - handler.mjs gzipped:      2,577 KiB → 1,331 KiB  (well under 3 MiB)
  - mermaid/katex/highlight.js refs in handler.mjs: 79 → 0

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: AndresL230

frontend/src/components/ChatPanel.tsx

@@ -1,8 +1,18 @@
 "use client";
 
 import React, { useEffect, useRef, useState } from "react";
+import dynamic from "next/dynamic";
 import { Icon } from "./Icon";
-import { MarkdownChat } from "./MarkdownChat";
+
+// MarkdownChat statically imports mermaid, katex, highlight.js, and the
+// remark/rehype stack. Static-importing it from a client component still
+// pulls those modules through next.config.ts → transpilePackages, which
+// bloats the OpenNext worker bundle on Cloudflare. Lazy-load with
+// ssr:false so the heavy markdown stack is a separate client chunk.
+const MarkdownChat = dynamic(
+  () => import("./MarkdownChat").then((m) => m.MarkdownChat),
+  { ssr: false, loading: () => null },
+);
 
 export type ChatRole = "user" | "assistant";
 export interface ChatMsg {

frontend/src/components/screens/Library.tsx

@@ -1,12 +1,19 @@
 "use client";
 import React from "react";
+import dynamic from "next/dynamic";
 import { createPortal } from "react-dom";
 import { TopBar } from "../TopBar";
 import { Icon } from "../Icon";
 import { Pill } from "../Pill";
 import { DocumentUploadModal } from "../DocumentUploadModal";
 import { LibraryGridSkeleton, LibraryListSkeleton } from "../Skeleton";
-import { MarkdownChat } from "../MarkdownChat";
+
+// Lazy-load to keep mermaid/katex/highlight.js out of the OpenNext
+// server bundle. See ChatPanel.tsx for the rationale.
+const MarkdownChat = dynamic(
+  () => import("../MarkdownChat").then((m) => m.MarkdownChat),
+  { ssr: false, loading: () => null },
+);
 import { useToast } from "../ToastProvider";
 import { useConfirm } from "@/lib/useConfirm";
 import { useIsMobile } from "@/lib/useIsMobile";

frontend/src/components/screens/Study.tsx

@@ -1,13 +1,20 @@
 "use client";
 import React from "react";
+import dynamic from "next/dynamic";
 import { useSearchParams } from "next/navigation";
 import { AnimatePresence, motion } from "framer-motion";
 import { TopBar } from "../TopBar";
 import { AIDisclaimerChip } from "../AIDisclaimerChip";
 import { Icon } from "../Icon";
 import { Pill } from "../Pill";
 import { CustomSelect } from "../CustomSelect";
-import { MarkdownChat } from "../MarkdownChat";
+
+// Lazy-load to keep mermaid/katex/highlight.js out of the OpenNext
+// server bundle. See ChatPanel.tsx for the rationale.
+const MarkdownChat = dynamic(
+  () => import("../MarkdownChat").then((m) => m.MarkdownChat),
+  { ssr: false, loading: () => null },
+);
 import { StudyGuideSkeleton, FlashcardsSkeleton } from "../Skeleton";
 import { useToast } from "../ToastProvider";
 import { useIsMobile } from "@/lib/useIsMobile";