Add no_item_validation decorator argument to parse and parse_cls

[maread99]

Resolves #6.

Summary

Adds a no_item_validation argument to the parse and parse_cls decorators to skip validation of container items for all parameters, e.g:

@parse(no_item_validation=True)
def f(
    a: list[str],
    b: dict[str, int],
    c: tuple[str, ...],
):
    ...

This has the same effect as including the NO_ITEM_VALIDATION constant to every parameter's Annotated metadata:

@parse
def f(
    a: Annotated[list[str], NO_ITEM_VALIDATION],
    b: Annotated[dict[str, int], NO_ITEM_VALIDATION],
    c: Annotated[tuple[str, ...], NO_ITEM_VALIDATION],
):
    ...

The container types themselves are still validated — only the item-level validation is skipped, at all levels of nesting.

Changes

• parse and parse_cls now support both the bare (@parse) and called (@parse(...)) forms. When invoked with arguments they return a functools.partial, preserving the existing bare-decorator behaviour.
• no_item_validation is threaded through validate_against_hints and validates_against_hint (including the Union recursion), reusing the same early-return path as the per-parameter NO_ITEM_VALIDATION constant.
• Updated the module docstring and the tutorial notebook to document the new argument.

Tests

Added three tests covering:

• @parse(no_item_validation=True) skipping item validation across container types (incl. nested containers), while still validating the container types themselves.
• @parse() (called form, default) still validating items.
• @parse_cls(no_item_validation=True) behaviour on a dataclass.

Full suite passes (pytest), ruff check/ruff format clean, and no new mypy errors introduced.

https://claude.ai/code/session_01Tu9LcAL1F5xrFpJSsEqLc3

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