feat: restructure conversion

[henryiii]

Restructure the way we convert. Better error messages.

[Copilot]

Pull Request Overview

This PR adds a to_project_table function that converts and validates dictionaries to PyProjectTable TypedDict at runtime. This enables runtime type checking of pyproject.toml data structures.

• Added to_project_table() function for runtime type validation
• Added _cast() helper function for recursive type checking
• Improved Python 3.10 compatibility by making typing_extensions.Required optional

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

File	Description
pyproject_metadata/project_table.py	Adds runtime type validation functions (to_project_table, _cast, is_typed_dict) and improves Required import handling for Python 3.10 compatibility
tests/test_project_table.py	Comprehensive test coverage for the new conversion function, including success and error cases
pyproject.toml	Adds linter exception for ERA001 (commented-out code) in project_table.py

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[Copilot]

Pull request overview

Copilot reviewed 8 out of 8 changed files in this pull request and generated 6 comments.

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[Copilot]

The fallback for ParamSpec and Concatenate on Python < 3.10 without typing_extensions will fail at runtime. On line 66, P.args and P.kwargs are accessed, but when ParamSpec is aliased to TypeVar (line 19), TypeVar instances don't have these attributes. Either add typing_extensions as a dependency for Python < 3.10, or implement a proper fallback class that provides args and kwargs attributes.

Suggested change

	ParamSpec = typing.TypeVar
	Concatenate = object
	try:
	from typing_extensions import Concatenate, ParamSpec
	except ImportError:
	def ParamSpec(name: str) -> typing.TypeVar:
	tv = typing.TypeVar(name)
	# Provide .args and .kwargs attributes so that annotations like
	# *args: P.args, **kwargs: P.kwargs do not fail at runtime.
	setattr(tv, "args", ())
	setattr(tv, "kwargs", {})
	return tv
	class Concatenate:
	"""Minimal runtime fallback for typing_extensions.Concatenate.
	This is only used in type annotations; returning the argument from
	__class_getitem__ is sufficient for annotations to evaluate.
	"""
	def __class_getitem__(cls, item):
	return item

[Copilot]

Implicit string concatenation. Maybe missing a comma?