test(parser): add property and fuzz coverage

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Summary

• add deterministic parser property tests for all registry permutations, generated malformed source tokens, stable failure taxonomy, and arbitrary-byte result invariants
• expose an internal registry-span dispatch seam so ordering can be tested without changing AuthLogParser
• add an optional Clang/libFuzzer parser target with a sanitized seed corpus
• add a bounded Ubuntu fuzz smoke job and document the verification route

Validation

• Windows Debug build and full CTest: 6/6 passed
• WSL/GCC clean build and full CTest: 6/6 passed
• targeted parser_properties CTest passed
• actionlint .github/workflows/ci.yml
• git diff --check
• local Markdown link validation
• privacy and secret-pattern scan

CI note

The local WSL environment does not include Clang. The new Ubuntu Parser fuzz smoke job is the authoritative libFuzzer compile/run gate for this PR.