feat: add TUI code block syntax highlighting (#1200) (thanks @vignesh07)

src/tui/theme/theme.test.ts

@@ -102,7 +102,8 @@ console.log(message);`;
       const result = markdownTheme.highlightCode!(code, "javascript");
 
       // Strip ANSI codes to verify content is preserved
-      const stripAnsi = (str: string) => str.replace(/\x1b\[[0-9;]*m/g, "");
+      const stripAnsi = (str: string) =>
+        str.replace(new RegExp(`${String.fromCharCode(27)}\\[[0-9;]*m`, "g"), "");
       expect(stripAnsi(result[0])).toBe(`const message = "Hello, World!";`);
       expect(stripAnsi(result[1])).toBe("console.log(message);");
     });

src/tui/theme/theme.ts

@@ -88,6 +88,7 @@ const syntaxTheme = {
  */
 function highlightCode(code: string, lang?: string): string[] {
   try {
+    // Auto-detect can be slow for very large blocks; prefer explicit language when available.
     // Check if language is supported, fall back to auto-detect
     const language = lang && supportsLanguage(lang) ? lang : undefined;
     const highlighted = highlight(code, {