Revert Mermaid lazy loading to fix E2E tests

The React.lazy approach was causing E2E tests to timeout. While it reduced
the main bundle slightly, the benefits don't outweigh the test failures.

Keeping the Shiki and tokenizer optimizations which provide the bulk
of the bundle size reduction without breaking tests.

Author: kylecarbs

src/components/Messages/MarkdownComponents.tsx

@@ -1,16 +1,12 @@
 import type { ReactNode } from "react";
-import React, { useState, useEffect, Suspense, lazy } from "react";
+import React, { useState, useEffect } from "react";
+import { Mermaid } from "./Mermaid";
 import {
   getShikiHighlighter,
   mapToShikiLang,
   SHIKI_THEME,
 } from "@/utils/highlighting/shikiHighlighter";
 
-// Lazy load Mermaid to keep it out of the main bundle
-// Dynamic import is intentional for code-splitting
-// eslint-disable-next-line no-restricted-syntax
-const Mermaid = lazy(() => import("./Mermaid").then((module) => ({ default: module.Mermaid })));
-
 interface CodeProps {
   node?: unknown;
   inline?: boolean;
@@ -137,11 +133,7 @@ export const markdownComponents = {
 
     // Handle mermaid diagrams specially
     if (!isInline && language === "mermaid") {
-      return (
-        <Suspense fallback={<div style={{ padding: "1rem" }}>Loading diagram...</div>}>
-          <Mermaid chart={childString} />
-        </Suspense>
-      );
+      return <Mermaid chart={childString} />;
     }
 
     // Code blocks with language - use async Shiki highlighting