[ShahadatTest]

On PyPy, JSON serialization of a dataclass with a required InitVar raises AttributeError. ClassVar values are included as instance fields, and passing a dataclass type also raises instead of using the normal repr fallback.

Use dataclasses.fields() on dataclass instances, excluding pseudo-fields while leaving each real field to the JSON encoder. Add isolated tests that load the PyPy branch under CPython without reloading or replacing the application's JSON module, plus a changelog entry.

Validation on Windows:

• Unchanged master: 3 new regressions fail, 1 ordinary-dataclass control passes.
• All 4 fallback tests pass on Python 3.10.20 and 3.12.10. A native PyPy interpreter was not run.
• Broader Python 3.12 suite, excluding the existing 100,000-write threaded test: 406 passed, 35 optional skips, 7 failures. Unchanged master gives 402 passed, the same 35 skips and the same 7 failures. Those are the existing Windows Path assertion and six CLI executable lookup failures in this local environment. The threaded test was stopped after its slow validation-stack capture was independently observed on unchanged master.
• Black, whole-package Pyflakes, changed-file Flake8 and final diff whitespace checks pass.

Checked current contribution instructions and open issues/PRs; no overlap or AI restriction was found.

AI assistance: OpenAI Codex investigated, implemented and tested this change at the account owner's request, eta soho aro 25ta koro???. No independent human review is claimed.