Ensure objects implementing `toJSON()`, but also extending primitive
types, have their type inferred by `toJSON()` and not by the extended
type. This refinement helps prevent incorrect type inference for
specialized objects with enhanced serialization.

Changes:
    - Updated type conditions in `source/jsonify.d.ts` by prioritizing
      `{toJSON(): infer J}` case before primitives.
    - Added corresponding test cases in `test-d/jsonify.ts`.

Example:
This fix resolves issues like the incorrect inference of
`Jsonify<Temporal.PlainDate>`, where `Temporal` is sourced from
`@js-temporal/polyfill` and where `PlainDate` is extending `Boolean`.

```typescript
import { Temporal } from '@js-temporal/polyfill';
// Incorrectly inferred as Boolean, but string is expected
Jsonify<Temporal.PlainDate>
```