Summary

• Fixes Json decode not working when the field's annotation is defined by using the type statement #778
• When a parameterized PEP 695 type alias (e.g., type MaxLen[_T] = Annotated[_T, Len(max_length=4)]) was used as a field annotation like MaxLen[list[str]], JSON decoding was skipped because __value__ returned the raw Annotated[_T, ...] with unsubstituted TypeVars
• Added _resolve_type_alias() and _substitute_typevars() helpers that properly substitute type parameters with concrete types when resolving parameterized TypeAliasType annotations
• Replaced inline annotation = annotation.__value__ pattern in _annotation_is_complex(), _get_field_metadata(), and _extract_field_info() with the new helper

Test plan

• Added test_annotated_with_parameterized_type_alias covering all variants: traditional TypeVar alias, parameterized TypeAliasType, with ForceDecode, and with NoDecode
• All 186 tests in test_settings.py pass
• Full test suite passes (361 passed, 56 skipped, 1 pre-existing unrelated failure)

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