Highlight returns SX tree, rendered to HTML/DOM by pipeline

highlight.sx now returns a list of (span :class "..." "text") elements
instead of a string. The rendering pipeline handles the rest:
- Server render-to-html: produces <span class="...">text</span>
- Client render-to-dom: produces DOM span elements
- Aser: serializes spans as SX for client rendering

Key fixes:
- hl-span uses (make-keyword "class") not :class (keywords evaluate
  to strings in list context)
- render-sx-tokens returns flat list of spans (no wrapper)
- hl-escape is identity (no escaping needed for tree values)
- highlight.sx added to browser bundle + platform loader
- ~docs/code renders src directly as child of pre

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

lib/highlight.sx

@@ -67,36 +67,7 @@
 
 (define hl-ws? (fn (c) (or (= c " ") (= c "\n") (= c "\t") (= c "\r"))))
 
-(define
-  hl-escape
-  (fn
-    (s)
-    (let
-      ((result "") (i 0) (len (string-length s)))
-      (let
-        loop
-        ()
-        (when
-          (< i len)
-          (let
-            ((c (substring s i (+ i 1))))
-            (set!
-              result
-              (str
-                result
-                (if
-                  (= c "\\")
-                  "\\\\"
-                  (if
-                    (= c "\"")
-                    "\\\""
-                    (if
-                      (= c "\n")
-                      "\\n"
-                      (if (= c "\t") "\\t" (if (= c "\r") "\\r" c)))))))
-            (set! i (+ i 1))
-            (loop))))
-      result)))
+(define hl-escape (fn (s) s))
 
 (define
   hl-span
@@ -104,8 +75,8 @@
     (class text)
     (if
       (= class "")
-      (str "(span \"" (hl-escape text) "\")")
-      (str "(span :class \"" class "\" \"" (hl-escape text) "\")"))))
+      (list (quote span) text)
+      (list (quote span) (make-keyword "class") class text))))
 
 (define
   tokenize-sx
@@ -309,9 +280,13 @@
   render-sx-tokens
   (fn
     (tokens)
-    (let
-      ((parts (map (fn (tok) (let ((kind (first tok)) (text (first (rest tok)))) (hl-span (get sx-token-classes kind "") text))) tokens)))
-      (str "(<> " (join " " parts) ")"))))
+    (map
+      (fn
+        (tok)
+        (let
+          ((cls (or (dict-get sx-token-classes (first tok)) "")))
+          (hl-span cls (nth tok 1))))
+      tokens)))
 
 (define highlight-sx (fn (code) (render-sx-tokens (tokenize-sx code))))
 
@@ -322,7 +297,4 @@
     (if
       (or (= lang "lisp") (= lang "sx") (= lang "sexp") (= lang "scheme"))
       (highlight-sx code)
-      (str
-        "(pre :class \"text-sm overflow-x-auto\" (code \""
-        (hl-escape code)
-        "\"))"))))
+      (list (quote code) code))))