test(crypto): expand is_uuid_like coverage for nibbles, Max, and non-hex characters

[vtushar06]

I added 8 test blocks to is_uuid_like. Core already passes all of them, so this is coverage, not a fix.

What is new:

• valid_max - the Max UUID (all f), RFC 9562 section 5.10, alongside the existing Nil case.
• valid_all_version_nibbles and valid_all_variant_nibbles - loops over 0-f at index 14 and index 19, pinning that is_uuid_like treats the version and variant as semantic fields, not syntactic constraints (RFC 9562 sections 4.1 and 4.2).
• invalid_underscore_separator, invalid_leading_plus, invalid_hex_radix_prefix, invalid_non_ascii_digit - characters that a lenient integer parser tolerates (_, +, 0x, a Unicode decimal digit) but HEXDIG does not. is_uuid_like rejects them through its byte-level hex check, unlike a checker that validates the hex content with an integer parser.
• invalid_trailing_newline - a complete UUID followed by \n.

How I checked the expected values: I compiled and ran every block against the real is_uuid_like before staging - all 8 pass.

RFC references: RFC 9562 sections 4, 4.1, 4.2, 5.9, 5.10.

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[cubic-dev-ai]

No issues found across 1 file

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[augmentcode]

🤖 Augment PR Summary

Summary: Expands unit test coverage for sourcemeta::core::is_uuid_like without changing production code.

Changes:

• Adds a valid_max test for the all-f (“Max”) UUID alongside the existing Nil/zero case.
• Adds loop-based tests that vary the version (index 14) and variant (index 19) nibbles across 0-f to assert they’re treated as semantic fields, not syntactic constraints.
• Adds negative tests for characters some integer parsers may accept (_, leading +, 0x prefix, non-ASCII digit) but HEXDIG should not.
• Adds a negative test for an otherwise-valid UUID with a trailing newline.
• Includes <string>/<string_view> needed by the new loop tests.

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[augmentcode]

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[jviotti]

Looks good but formatting and DCO are failing!

[vtushar06]

Hey @jviotti, Pr is ready for another look.