js-on-sx: String wrapper objects + number-to-string sci notation expansion

- js-to-string: return __js_string_value__ for String wrapper dicts
- js-loose-eq: coerce String wrapper objects to primitive before compare
- String.__callable__: set __js_string_value__ + length on 'this' when called as constructor
- js-expand-sci-notation: new helper converts mantissa+exp to decimal or integer form
- js-number-to-string: expand 1e-06→0.000001, 1e+06→1000000; fix 1e+21 (was 1e21)
- String test262 subset: 45→58/100

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

lib/js/test262-scoreboard.json

@@ -1,72 +1,34 @@
 {
   "totals": {
-    "pass": 202,
-    "fail": 85,
-    "skip": 1597,
-    "timeout": 13,
-    "total": 1897,
-    "runnable": 300,
-    "pass_rate": 67.3
+    "pass": 58,
+    "fail": 33,
+    "skip": 1130,
+    "timeout": 9,
+    "total": 1230,
+    "runnable": 100,
+    "pass_rate": 58.0
   },
   "categories": [
-    {
-      "category": "built-ins/Math",
-      "total": 327,
-      "pass": 82,
-      "fail": 17,
-      "skip": 227,
-      "timeout": 1,
-      "pass_rate": 82.0,
-      "top_failures": [
-        [
-          "Test262Error (assertion failed)",
-          17
-        ],
-        [
-          "Timeout",
-          1
-        ]
-      ]
-    },
-    {
-      "category": "built-ins/Number",
-      "total": 340,
-      "pass": 77,
-      "fail": 19,
-      "skip": 240,
-      "timeout": 4,
-      "pass_rate": 77.0,
-      "top_failures": [
-        [
-          "Test262Error (assertion failed)",
-          19
-        ],
-        [
-          "Timeout",
-          4
-        ]
-      ]
-    },
     {
       "category": "built-ins/String",
       "total": 1223,
-      "pass": 43,
-      "fail": 49,
+      "pass": 58,
+      "fail": 33,
       "skip": 1123,
-      "timeout": 8,
-      "pass_rate": 43.0,
+      "timeout": 9,
+      "pass_rate": 58.0,
       "top_failures": [
         [
           "Test262Error (assertion failed)",
-          42
+          28
         ],
         [
           "Timeout",
-          8
+          9
         ],
         [
-          "TypeError: not a function",
-          3
+          "Unhandled: Not callable: \\\\\\",
+          1
         ],
         [
           "ReferenceError (undefined symbol)",
@@ -92,15 +54,15 @@
   "top_failure_modes": [
     [
       "Test262Error (assertion failed)",
-      78
+      28
     ],
     [
       "Timeout",
-      13
+      9
     ],
     [
-      "TypeError: not a function",
-      3
+      "Unhandled: Not callable: \\\\\\",
+      1
     ],
     [
       "ReferenceError (undefined symbol)",
@@ -111,7 +73,7 @@
       1
     ],
     [
-      "Unhandled: Not callable: \\\\\\",
+      "TypeError: not a function",
       1
     ],
     [
@@ -120,6 +82,6 @@
     ]
   ],
   "pinned_commit": "d5e73fc8d2c663554fb72e2380a8c2bc1a318a33",
-  "elapsed_seconds": 102.4,
-  "workers": 2
+  "elapsed_seconds": 37.7,
+  "workers": 7
 }