Stop uuid() from accepting urn:/braced forms via dead-code fallback

[mathewOracle]

The bug

uuid() builds its result like this:

try:
    return UUID(value) or re.match(
        r"^[0-9a-fA-F]{8}-([0-9a-fA-F]{4}-){3}[0-9a-fA-F]{12}$", value
    )
except ValueError:
    return False

A successfully-parsed UUID object is always truthy (no __bool__/__len__), so or re.match(...) is unreachable dead code. The real acceptance criteria has always been "whatever UUID() accepts", not the regex the code appears to enforce — and UUID() accepts a lot more than this validator documents or tests:

>>> uuid('urn:uuid:2bc1c94f-0deb-43e9-92a1-4775189ec9f8')
True   # should be rejected
>>> uuid('{2bc1c94f-0deb-43e9-92a1-4775189ec9f8}')
True   # should be rejected

Neither form is in the docstring, tests, or (as far as I could find via GitHub search) any prior issue/PR. The closest related history is #112/#175, about accepting hyphen-less hex — that's an intentional, tested feature this fix keeps working.

The fix

Drop the UUID()-based parsing and validate directly with a regex, extended to also accept the already-tested hyphen-less form:

return bool(re.match(r"^[0-9a-fA-F]{8}-?([0-9a-fA-F]{4}-?){3}[0-9a-fA-F]{12}$", value))

This is a strict subset of what the old code's own regex/docstring described as valid — I deliberately didn't try to guess at any broader intended behavior (e.g. version-nibble checks despite the "UUID-v4" docstring wording), since that would be speculative about intent rather than fixing a demonstrated bug.

Verification

• All 8 existing test_uuid.py cases pass unchanged.
• Added 2 regression cases (urn:uuid:..., {...}) to the existing invalid-input parametrize list. Confirmed they fail against the unpatched code (reverted locally to double-check) and pass with the fix.
• Non-string inputs (123, 1.5, True, ['x'], {'a': 1}, None) still resolve to ValidationError rather than crashing — TypeError from re.match on a non-string is already caught by @validator in utils.py, so no new exception handling needed.
• Full suite: pytest tests/ — 897 passed (895 baseline + 2 new), 0 regressions.
• pytest --doctest-modules src/validators/ — 57 passed.
• ruff format --check, ruff check, pyright all clean on the changed files — matches this repo's pycqa.yaml CI job exactly.

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Found via targeted review of validator internals (differential testing across the library's public functions caught the over-permissive acceptance surface), not from a filed issue. AI-assisted (Code Puppy); reproduced, root-caused, fixed, and verified bidirectionally before opening this.