HS: fix hs-for-each to handle dicts and nil collections

hs-for-each now converts dicts to key lists and nil to empty list
before iterating, fixing regression where for-in loops over object
properties stopped working after the for-each → hs-for-each switch.

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

lib/hyperscript/runtime.sx

@@ -377,19 +377,21 @@
   hs-for-each
   (fn
     (fn-body collection)
-    (define
-      do-loop
-      (fn
-        (items)
-        (when
-          (not (empty? items))
-          (let
-            ((signal (guard (e (true (str e))) (do (fn-body (first items)) nil))))
-            (cond
-              ((= signal "hs-break") nil)
-              ((= signal "hs-continue") (do-loop (rest items)))
-              (true (do-loop (rest items))))))))
-    (when (list? collection) (do-loop collection))))
+    (let
+      ((items (cond ((list? collection) collection) ((dict? collection) (keys collection)) ((nil? collection) (list)) (true (list)))))
+      (define
+        do-loop
+        (fn
+          (remaining)
+          (when
+            (not (empty? remaining))
+            (let
+              ((signal (guard (e (true (str e))) (do (fn-body (first remaining)) nil))))
+              (cond
+                ((= signal "hs-break") nil)
+                ((= signal "hs-continue") (do-loop (rest remaining)))
+                (true (do-loop (rest remaining))))))))
+      (do-loop items))))
 
 (define
   hs-fetch