js-on-sx: native prototypes carry wrapped primitive marker

Per ES, Boolean.prototype is a Boolean wrapper around false,
Number.prototype wraps 0, String.prototype wraps "". So
Boolean.prototype == false (loose-eq unwraps), and
Object.prototype.toString.call(Number.prototype) ===
"[object Number]". Set __js_*_value__ on each in post-init.
built-ins/Boolean: 23/27 → 24/27, String: 80/99 → 84/99.
conformance.sh: 148/148.

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.
 
+- 2026-05-08 — **Native prototypes carry the wrapped primitive marker.** Per ES, `Boolean.prototype` is a Boolean wrapper around `false`, `Number.prototype` wraps `0`, `String.prototype` wraps `""`. So `Boolean.prototype == false` (loose-eq unwraps), `Object.prototype.toString.call(Number.prototype) === "[object Number]"`, etc. Set `__js_boolean_value__: false` / `__js_number_value__: 0` / `__js_string_value__: ""` on the respective prototypes in the post-init block. built-ins/Boolean: 23/27 → 24/27, String: 80/99 → 84/99. conformance.sh: 148/148.
+
 - 2026-05-08 — **`js-to-number` throws TypeError when valueOf+toString both return non-primitive.** Mirrors the earlier `js-to-string` fix. Per spec, `Number(obj)` must throw if `ToPrimitive` cannot extract a primitive. Was returning `NaN` silently. Replaced the inner `(js-nan-value)` fallback with `(raise (js-new-call TypeError ...))`. built-ins/Number: 45/50 → 46/50. conformance.sh: 148/148.
 
 - 2026-05-08 — **`Array.prototype` / `Number.prototype` / etc. inherit from `Object.prototype`.** Per ES, every native prototype's `[[Prototype]]` is `Object.prototype` (and `Function.prototype.[[Prototype]]` is also `Object.prototype`). Was missing those `__proto__` links, so `Object.prototype.isPrototypeOf(Boolean.prototype)` returned false (the explicit isPrototypeOf walks `__proto__`, not the recent fallback). Added 5 `dict-set!` lines to the post-init block at the end of `runtime.sx`. built-ins/Boolean: 22/27 → 23/27, built-ins/Number: 44/50 → 45/50. conformance.sh: 148/148.