Add syntax highlighting for Racket, Elisp, and Scheme

Add language alias mapping in highlight_code() to map:
- racket, rkt -> lisp
- elisp, emacs-lisp -> lisp
- scheme -> lisp
- common-lisp, cl -> lisp
- shell, sh, zsh, dockerfile -> bash

Syntect's built-in Lisp syntax handles all Lisp-family languages well.
Added test to verify the aliases work correctly.

crates/g3-cli/src/streaming_markdown.rs

@@ -799,8 +799,22 @@ fn is_potential_delimiter_start(ch: char) -> bool {
 
 /// Highlight code with syntect.
 fn highlight_code(code: &str, lang: Option<&str>) -> String {
+    // Map language aliases to syntect-recognized names
+    let normalized_lang = lang.map(|l| match l.to_lowercase().as_str() {
+        // Lisp family - syntect's "Lisp" syntax handles these well
+        "racket" | "rkt" => "lisp",
+        "elisp" | "emacs-lisp" => "lisp",
+        "scheme" => "lisp",
+        "common-lisp" | "cl" => "lisp",
+        // Other common aliases
+        "shell" | "sh" => "bash",
+        "zsh" => "bash",
+        "dockerfile" => "bash",
+        _ => l,
+    });
+
     let syntax = lang
-        .and_then(|l| SYNTAX_SET.find_syntax_by_token(l))
+        .and_then(|_| normalized_lang.and_then(|l| SYNTAX_SET.find_syntax_by_token(l)))
         .unwrap_or_else(|| SYNTAX_SET.find_syntax_plain_text());
     
     let theme = &THEME_SET.themes["base16-ocean.dark"];

crates/g3-cli/tests/streaming_markdown_test.rs

@@ -1536,3 +1536,53 @@ fn stress_test_pathological() {
         fmt = make_formatter();
     }
 }
+
+#[test]
+fn test_language_aliases() {
+    let mut fmt = make_formatter();
+    
+    // Test Racket code block
+    let racket_code = r#"```racket
+(define (factorial n)
+  (if (<= n 1)
+      1
+      (* n (factorial (- n 1)))))
+```
+"#;
+    let output = fmt.process(racket_code);
+    let remaining = fmt.finish();
+    let full = format!("{}{}", output, remaining);
+    // Should have ANSI codes (syntax highlighting applied)
+    assert!(full.contains("\x1b["), "Racket should be syntax highlighted");
+    assert!(full.contains("factorial"));
+    
+    // Test elisp code block
+    let mut fmt = make_formatter();
+    let elisp_code = r#"```elisp
+(defun hello-world ()
+  "Print hello world."
+  (interactive)
+  (message "Hello, World!"))
+```
+"#;
+    let output = fmt.process(elisp_code);
+    let remaining = fmt.finish();
+    let full = format!("{}{}", output, remaining);
+    assert!(full.contains("\x1b["), "Elisp should be syntax highlighted");
+    assert!(full.contains("hello-world"));
+    
+    // Test scheme code block  
+    let mut fmt = make_formatter();
+    let scheme_code = r#"```scheme
+(define (map f lst)
+  (if (null? lst)
+      '()
+      (cons (f (car lst))
+            (map f (cdr lst)))))
+```
+"#;
+    let output = fmt.process(scheme_code);
+    let remaining = fmt.finish();
+    let full = format!("{}{}", output, remaining);
+    assert!(full.contains("\x1b["), "Scheme should be syntax highlighted");
+}