feat: port test_constructor to CTS (#29)

Exercises napi_define_class with method, data value, accessor, and
static property descriptors. Includes null-argument tests for
napi_define_class via test_null.c/test_null.js.

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>
Co-authored-by: Chengzhong Wu <legendecas@gmail.com>

Author: 3 people

PORTING.md

@@ -52,6 +52,8 @@ Tests covering the engine-specific part of Node-API, defined in `js_native_api.h
 | `test_cannot_run_js`         | Not ported | Medium     |
 | `test_constructor`           | Ported ✅  | Medium     |
 | `test_conversions`           | Ported ✅  | Medium     |
+| `test_constructor`           | Ported ✅  | Medium     |
+| `test_conversions`           | Not ported | Medium     |
 | `test_dataview`              | Not ported | Medium     |
 | `test_date`                  | Ported ✅  | Easy       |
 | `test_error`                 | Ported ✅  | Medium     |