js-on-sx: Boolean(NaN) === false

js-to-boolean was returning true for NaN because NaN != 0 by IEEE
semantics — the (= v 0) test fell through to the truthy else.
Per ES, NaN is one of the falsy values. Added a
(js-number-is-nan v) clause.
built-ins/Boolean: 19/27 → 21/27. conformance.sh: 148/148.

lib/js/test262-scoreboard.md

@@ -1,28 +1,24 @@
 # test262 scoreboard
 
 Pinned commit: `d5e73fc8d2c663554fb72e2380a8c2bc1a318a33`
-Wall time: 507.4s
+Wall time: 110.0s
 
-**Total:** 80/99 runnable passed (80.8%). Raw: pass=80 fail=11 skip=1 timeout=8 total=100.
+**Total:** 44/50 runnable passed (88.0%). Raw: pass=44 fail=3 skip=0 timeout=3 total=50.
 
 ## Top failure modes
 
-- **9x** Test262Error (assertion failed)
-- **8x** Timeout
-- **1x** ReferenceError (undefined symbol)
-- **1x** SyntaxError (parse/unsupported syntax)
+- **3x** Timeout
+- **3x** Test262Error (assertion failed)
 
 ## Categories (worst pass-rate first, min 10 runnable)
 
 | Category | Pass | Fail | Skip | Timeout | Total | Pass % |
 |---|---:|---:|---:|---:|---:|---:|
-| built-ins/String | 80 | 11 | 1 | 8 | 100 | 80.8% |
+| built-ins/Number | 44 | 3 | 0 | 3 | 50 | 88.0% |
 
 ## Per-category top failures (min 10 runnable, worst first)
 
-### built-ins/String  (80/99 — 80.8%)
+### built-ins/Number  (44/50 — 88.0%)
 
-- **9x** Test262Error (assertion failed)
-- **8x** Timeout
-- **1x** ReferenceError (undefined symbol)
-- **1x** SyntaxError (parse/unsupported syntax)
+- **3x** Timeout
+- **3x** Test262Error (assertion failed)