Bad plain object handling as PromiseRejectionEvent reason

Currently when a promise is rejected with a plain object instead of an Error `Promise.reject({ code: 42, detail: 'oops' })`, the catcher loses the object content - `String(obj)` produces `"[object Object]"`.

The console catcher also falls back to `event.reason?.message || String(event.reason)`, which either picks up an accidental `message` property or produces the same useless string.