js-on-sx: Number/String.prototype methods carry spec lengths + names

plans/js-on-sx.md

@@ -158,6 +158,8 @@ Each item: implement → tests → update progress. Mark `[x]` when tests green.
 
 Append-only record of completed iterations. Loop writes one line per iteration: date, what was done, test count delta.
 
+- 2026-05-09 — **`Number.prototype` and `String.prototype` methods carry spec lengths and names.** Same shape as the earlier Function.prototype fix. Number.prototype.{toFixed/toExponential/toPrecision/toString/valueOf/toLocaleString} were bare `(fn ...)` lambdas → length 0 → tests assert e.g. `Number.prototype.toExponential.length === 1`. Wrapped each in a dict-with-`__callable__` with `:length` and `:name`. For String.prototype, `js-string-proto-fn` was a single helper applied to ~30 method names; added `js-string-proto-fn-length` (lookup table for spec-defined lengths: `concat:1`, `indexOf:1`, `slice:2`, `substring:2`, `replace:2`, etc.) and changed the helper to return the dict form, so all string methods now report correctly. Result: built-ins/Number/prototype 18/30 → 20/30, String/prototype 18/30 → 21/30. Number 26/30 holds, String 29/30. conformance.sh: 148/148.
+
 - 2026-05-09 — **`Boolean.prototype.toString`/`valueOf` throw TypeError on non-Boolean receivers.** Per spec, both methods are not generic — calling them with a `this` that isn't a Boolean primitive or wrapper must throw TypeError. Was silently returning `"true"`/`"false"` based on whether the receiver was truthy (`s1.toString = Boolean.prototype.toString; s1.toString()` returned `"true"` for any non-empty string instead of throwing). Added an `else (raise (js-new-call TypeError ...))` branch to both prototype methods. Result: built-ins/Boolean 28/30 → 29/30. Object 30/30 holds. conformance.sh: 148/148.
 
 - 2026-05-09 — **`Array.prototype.reduce`/`reduceRight` callback receives `(acc, cur, idx, array)`.** Was calling `(f acc cur)` — only two args, no index, no source array. Per spec the reducer signature is `(accumulator, currentValue, currentIndex, array)`. Updated `js-list-reduce-loop` and `js-list-reduce-right-loop` to call via `js-call-with-this js-undefined f (list acc cur i arr)`. Result: built-ins/Array/prototype/reduce 6/30 → 8/30, reduceRight 6/30 → 8/30. Object 30/30 holds. conformance.sh: 148/148.