js-on-sx: array-like receivers for Array.prototype.* methods

Array.prototype.slice.call({length:3, 0:41, 1:42, 2:43}) used to crash with
'Not callable: {dict}' because js-array-proto-fn passed the dict straight
into js-invoke-method, which then tried (append! dict x) etc.

Now js-array-proto-fn converts dict-with-length receivers to a list via
js-arraylike-to-list before dispatch. Mutation methods (push/pop/shift/
reverse/sort/fill) still require a real list — array-likes only work for
read-only methods.

Targets the 455x 'Not callable: {:length N :0 v1 :1 v2 ...}' scoreboard item.

6 new unit tests, 459/461 total.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

lib/js/runtime.sx

@@ -1799,6 +1799,37 @@
           result))
       (else (list)))))
 
+(define
+  js-arraylike-to-list
+  (fn
+    (v)
+    (cond
+      ((list? v) v)
+      ((= (type-of v) "string") (js-string-to-list v 0 (list)))
+      ((dict? v)
+        (let
+          ((n-val (get v "length")))
+          (if
+            (or (= n-val nil) (js-undefined? n-val))
+            (list)
+            (let
+              ((n (js-to-number n-val)))
+              (js-arraylike-to-list-loop v 0 n (list))))))
+      (else (list)))))
+
+(define
+  js-arraylike-to-list-loop
+  (fn
+    (v i n acc)
+    (if
+      (>= i n)
+      acc
+      (let
+        ((val (get v (str i))))
+        (do
+          (append! acc (if (= val nil) :js-undefined val))
+          (js-arraylike-to-list-loop v (+ i 1) n acc))))))
+
 (define
   js-string-to-list
   (fn
@@ -1933,7 +1964,11 @@
     (name)
     (fn
       (&rest args)
-      (let ((this-val (js-this))) (js-invoke-method this-val name args)))))
+      (let
+        ((this-val (js-this)))
+        (let
+          ((recv (cond ((list? this-val) this-val) ((and (dict? this-val) (contains? (keys this-val) "length")) (js-arraylike-to-list this-val)) (else this-val))))
+          (js-invoke-method recv name args))))))
 
 (define
   js-array-from