Imported CJS function-constructor loses its own .name (decimal.js clone() shape): constructor.name is empty, Node says "Decimal"

[proggeramlug]

Found while validating the removal of the native decimal.js binding (#10684) — with the binding
gone, import Decimal from "decimal.js" now compiles the real npm package from source (via #10699).
Every value checked matches Node 26.5.1 exactly (1/3, 10/4, the large multiplication that used to
abort the process, instanceof, sqrt, pow, toFixed, toPrecision, cmp, chained arithmetic) —
except constructor.name, which is empty instead of "Decimal".

Reproduction

{ "dependencies": { "decimal.js": "^10.6.0" }, "type": "module" }

import Decimal from "decimal.js";
const d = new Decimal(5);
console.log(d instanceof Decimal);       // true on both (fixed by #10477)
console.log(d.constructor.name);         // Node: "Decimal"   Perry: ""
console.log((Decimal as any).name);      // Node: "Decimal"   Perry: ""

Root cause (as far as I traced it)

decimal.js's real source has no class Decimal; it is an ES5-style function constructor built by a
clone() factory and exported CommonJS-style (module.exports = Decimal;, decimal.js:4935) — the
same shape #10477 already tracked for instanceof (now fixed).

Isolated repros:

• A function constructor built by a same-file factory (function clone() { function Decimal(v) {...} return Decimal; }) — .name and .constructor.name are both correct.
• The same shape with the prototype wholesale-replaced (Decimal.prototype = { constructor: Decimal, ... }, matching decimal.js exactly) in the same file — still correct.
• The same shape moved to a separate module and exported via module.exports = Decimal (CJS),
  then imported with import Decimal from "./lib.js" — Decimal.name itself is already empty
  before .constructor even enters the picture.

So the loss happens specifically in the CJS-import interop path for a plain (non-class) function
value: whatever rebinds the CJS export at the import site is not preserving the underlying function
object's own .name. instanceof (#10477) and ordinary calls/construction work fine through the same
path; only the .name property is lost.

Impact

Any npm package (CJS or UMD, decimal.js/bignumber.js among them) that exports an ES5-style function
constructor and whose callers inspect .name / .constructor.name (error reporting, assert-style
type tags, some validation/serialization libraries) will see an empty string where Node reports the
real name.

Not fixed by, and not caused by, #10684's binding removal — decimal.js's own arithmetic, instanceof,
and everything else checked in that PR's acceptance test match Node exactly.