Rename frozen_field to field with frozen parameter

[Glinte]

Summary

• introduce field(frozen=True) helper to create immutable dataclass fields
• update documentation and tests to use the new field API

Testing

• ruff check
• pytest

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https://chatgpt.com/codex/tasks/task_e_68947a2bae0c8322b6eb2b5738e423c9

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[Copilot]

Pull Request Overview

This PR replaces the frozen_field() function with a more unified field(frozen=True) API that mimics the standard dataclasses API. The change makes the library more intuitive by providing a single field function with an optional frozen parameter instead of requiring a separate function for frozen fields.

• Introduce new field() function with frozen parameter to replace frozen_field()
• Update all tests and documentation to use the new unified API
• Maintain backward compatibility by keeping the frozen field functionality intact

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
semimutable/init.py	Implements new unified field() function with frozen parameter and updates internal documentation
tests/test_semimutable_dataclass.py	Updates test cases to use field(frozen=True) instead of frozen_field()
tests/test_identical_behaviour.py	Updates behavioral comparison tests to use new API
README.md	Updates usage documentation to demonstrate new field(frozen=True) syntax