fix: Add missing v2 constructor overrides

[dangotbanned]

What type of PR is this? (check all applicable)

• 💾 Refactor
• ✨ Feature
• 🐛 Bug Fix
• 🔧 Optimization
• 📝 Documentation
• ✅ Test
• 🐳 Other

Related issues

• Fixes feat: Add Series.from_iterable #2933 (comment)
• Part of API: io functions for v2 #2116

Checklist

• Code follows style guide (ruff)
• Tests added
• Documented the changes

If you have comments or can explain your changes, please do so below

• (fix: Add missing v2 constructor overrides)
• (test: Add v2 tests)

[dangotbanned]

Very important bit that I missed before 😞

It might make more sense to use what I did for Namespace, where this is enforced at subclass-defintion-time

narwhals/narwhals/_namespace.py

Lines 172 to 186 in b4f1a47

	class Namespace(Generic[CompliantNamespaceT_co]):
	_compliant_namespace: CompliantNamespaceT_co
	_version: ClassVar[Version] = Version.MAIN
	def __init__(self, namespace: CompliantNamespaceT_co, /) -> None:
	self._compliant_namespace = namespace
	def __init_subclass__(cls, *args: Any, version: Version, **kwds: Any) -> None:
	super().__init_subclass__(*args, **kwds)
	if isinstance(version, Version):
	cls._version = version
	else:
	msg = f"Expected {Version} but got {type(version).__name__!r}"
	raise TypeError(msg)

[dangotbanned]

I marked as bug: incorrect result because v2.{DataFrame,Series}.from_*(...) didn't preserve the Version but v1 did.

I expect that could have some confusing consequences, so hopefully this can make the next release 🤞

[MarcoGorelli]