js-on-sx: wrapper constructor-detection, Array.prototype.toString, >>> operator

Number.__callable__ and String.__callable__ now check this.__proto__ ===
Number/String.prototype before writing wrapper slots, preventing false-positive
mutation when called as plain function. js-to-number extended to unwrap
wrapper dicts and call valueOf/toString for plain objects. Array.prototype.toString
replaced with a direct js-list-join implementation (eliminates infinite recursion
via js-invoke-method on dict-based arrays). >>> added to transpiler + runtime.

String test262 subset: 62→66/100. 529/530 unit, 147/148 slice.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

lib/js/test262-scoreboard.json

@@ -1,42 +1,42 @@
 {
   "totals": {
-    "pass": 62,
-    "fail": 29,
+    "pass": 66,
+    "fail": 25,
     "skip": 1130,
     "timeout": 9,
     "total": 1230,
     "runnable": 100,
-    "pass_rate": 62.0
+    "pass_rate": 66.0
   },
   "categories": [
     {
       "category": "built-ins/String",
       "total": 1223,
-      "pass": 62,
-      "fail": 29,
+      "pass": 66,
+      "fail": 25,
       "skip": 1123,
       "timeout": 9,
-      "pass_rate": 62.0,
+      "pass_rate": 66.0,
       "top_failures": [
         [
           "Test262Error (assertion failed)",
-          24
+          14
         ],
         [
           "Timeout",
           9
         ],
         [
-          "Unhandled: Not callable: \\\\\\",
-          1
+          "TypeError: not a function",
+          6
         ],
         [
           "ReferenceError (undefined symbol)",
-          1
+          2
         ],
         [
-          "SyntaxError (parse/unsupported syntax)",
-          1
+          "Unhandled: Not callable: \\\\\\",
+          2
         ]
       ]
     },
@@ -54,34 +54,30 @@
   "top_failure_modes": [
     [
       "Test262Error (assertion failed)",
-      24
+      14
     ],
     [
       "Timeout",
       9
     ],
     [
-      "Unhandled: Not callable: \\\\\\",
-      1
+      "TypeError: not a function",
+      6
     ],
     [
       "ReferenceError (undefined symbol)",
-      1
+      2
+    ],
+    [
+      "Unhandled: Not callable: \\\\\\",
+      2
     ],
     [
       "SyntaxError (parse/unsupported syntax)",
       1
-    ],
-    [
-      "TypeError: not a function",
-      1
-    ],
-    [
-      "Unhandled: js-transpile-binop: unsupported op: >>>\\",
-      1
     ]
   ],
   "pinned_commit": "d5e73fc8d2c663554fb72e2380a8c2bc1a318a33",
-  "elapsed_seconds": 40.5,
-  "workers": 7
+  "elapsed_seconds": 157.9,
+  "workers": 1
 }