js-on-sx: js-to-string emits comma-joined elements for SX lists

String([1,2,3]) was returning "(1 2 3)" (the SX (str v) fallback in
js-to-string fell through for SX lists). Replaced the fallback with
a list-typed branch that delegates to (js-list-join v ","). Fixes
String(arr), "" + arr, and any implicit array-to-string coercion.
built-ins/String: 65/99 → 67/99. conformance.sh: 148/148.

lib/js/runtime.sx

@@ -1231,7 +1231,7 @@
                           "[object Object]"))
                       (js-to-string result)))
                   "[object Object]"))))
-          (str v))))))
+          (if (= (type-of v) "list") (js-list-join v ",") (str v)))))))
 
 (define
   js-template-concat

lib/js/test262-scoreboard.json

@@ -1,34 +1,30 @@
 {
   "totals": {
-    "pass": 65,
-    "fail": 28,
+    "pass": 67,
+    "fail": 19,
     "skip": 1,
-    "timeout": 6,
+    "timeout": 13,
     "total": 100,
     "runnable": 99,
-    "pass_rate": 65.7
+    "pass_rate": 67.7
   },
   "categories": [
     {
       "category": "built-ins/String",
       "total": 100,
-      "pass": 65,
-      "fail": 28,
+      "pass": 67,
+      "fail": 19,
       "skip": 1,
-      "timeout": 6,
-      "pass_rate": 65.7,
+      "timeout": 13,
+      "pass_rate": 67.7,
       "top_failures": [
         [
           "Test262Error (assertion failed)",
-          16
-        ],
-        [
-          "TypeError: not a function",
-          8
+          15
         ],
         [
           "Timeout",
-          6
+          13
         ],
         [
           "Unhandled: Not callable: \\\\\\",
@@ -37,6 +33,10 @@
         [
           "ReferenceError (undefined symbol)",
           1
+        ],
+        [
+          "SyntaxError (parse/unsupported syntax)",
+          1
         ]
       ]
     }
@@ -44,15 +44,11 @@
   "top_failure_modes": [
     [
       "Test262Error (assertion failed)",
-      16
-    ],
-    [
-      "TypeError: not a function",
-      8
+      15
     ],
     [
       "Timeout",
-      6
+      13
     ],
     [
       "Unhandled: Not callable: \\\\\\",
@@ -68,6 +64,6 @@
     ]
   ],
   "pinned_commit": "d5e73fc8d2c663554fb72e2380a8c2bc1a318a33",
-  "elapsed_seconds": 353.1,
+  "elapsed_seconds": 580.2,
   "workers": 1
 }

lib/js/test262-scoreboard.md

@@ -1,15 +1,14 @@
 # test262 scoreboard
 
 Pinned commit: `d5e73fc8d2c663554fb72e2380a8c2bc1a318a33`
-Wall time: 353.1s
+Wall time: 580.2s
 
-**Total:** 65/99 runnable passed (65.7%). Raw: pass=65 fail=28 skip=1 timeout=6 total=100.
+**Total:** 67/99 runnable passed (67.7%). Raw: pass=67 fail=19 skip=1 timeout=13 total=100.
 
 ## Top failure modes
 
-- **16x** Test262Error (assertion failed)
-- **8x** TypeError: not a function
-- **6x** Timeout
+- **15x** Test262Error (assertion failed)
+- **13x** Timeout
 - **2x** Unhandled: Not callable: \\\
 - **1x** ReferenceError (undefined symbol)
 - **1x** SyntaxError (parse/unsupported syntax)
@@ -18,14 +17,14 @@ Wall time: 353.1s
 
 | Category | Pass | Fail | Skip | Timeout | Total | Pass % |
 |---|---:|---:|---:|---:|---:|---:|
-| built-ins/String | 65 | 28 | 1 | 6 | 100 | 65.7% |
+| built-ins/String | 67 | 19 | 1 | 13 | 100 | 67.7% |
 
 ## Per-category top failures (min 10 runnable, worst first)
 
-### built-ins/String  (65/99 — 65.7%)
+### built-ins/String  (67/99 — 67.7%)
 
-- **16x** Test262Error (assertion failed)
-- **8x** TypeError: not a function
-- **6x** Timeout
+- **15x** Test262Error (assertion failed)
+- **13x** Timeout
 - **2x** Unhandled: Not callable: \\\
 - **1x** ReferenceError (undefined symbol)
+- **1x** SyntaxError (parse/unsupported syntax)