Add missing reference-data and special-forms-data helpers

These were lost during an earlier sx_replace_node edit. Both use
case expressions to route slugs to the correct data tables.

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

sx/sx/data/helpers.sx

@@ -51,6 +51,17 @@
 
 (define primitives-data (fn () primitives-by-category))
 
+(define
+  special-forms-data
+  (fn
+    ()
+    (let
+      ((source (read-spec-file "special-forms.sx")))
+      (if
+        (starts-with? source ";;")
+        {:categories (list)}
+        (categorize-special-forms (parse source))))))
+
 (define
   _spec-search-dirs
   (fn
@@ -74,6 +85,26 @@
         (_spec-search-dirs))
       (or result (str ";; spec file not found: " filename)))))
 
+(define
+  reference-data
+  (fn
+    (slug)
+    (let
+      ((raw-data (case slug "attributes" {:req-attrs request-attrs :beh-attrs behavior-attrs :uniq-attrs sx-unique-attrs} "headers" {:req-headers request-headers :resp-headers response-headers} "events" {:events-list events-list} "js-api" {:js-api-list js-api-list} :else {:req-attrs request-attrs :beh-attrs behavior-attrs :uniq-attrs sx-unique-attrs}))
+        (detail-keys
+          (case
+            slug
+            "attributes"
+            (keys attr-details)
+            "headers"
+            (keys header-details)
+            "events"
+            (keys event-details)
+            "js-api"
+            (list)
+            :else (keys attr-details))))
+      (build-reference-data slug raw-data detail-keys))))
+
 (define
   attr-detail-data
   (fn (slug) (build-attr-detail slug (get attr-details slug))))