[iliaal]

Summary

PHP converts numeric-string array keys to integers. Cast the delimiter keys back to strings at the two strict-comparison sites so numeric symmetric nickname delimiters obey the same boundary rules as other delimiters.

• John 0foo,do,bar0 Smith with 0 => '0' no longer produces a false standalone credential ambiguity.
• Smith0, John0 retains its structural comma and surname-first interpretation instead of treating a mid-token 0 as a nickname opener.
• Add 22 regression cases covering digits and multi-character numeric keys, valid nickname spans, mid-token openers/closers, unmatched delimiters and credentials outside a span. Include the required Unreleased entry.

Validation

Rebased after #23 merged onto 612656f5ccb5b2aaf0c89929ccf246bea77e1851; inspected current README, configuration, issues and open PRs (none), and verified every tracked base blob. No repository AGENTS or skills are present.

• PHP 8.4.26: full suite 1388 tests, 4012 assertions, all pass with 256 MiB memory limit.
• New tests: 22 tests, 122 assertions pass; unchanged final tests fail all 22 when the two production files are reverted to current base.
• PHPStan level 9 and PHP 8.5 configuration: pass. PHP-CS-Fixer dry run, whitespace and README/baseline/deprecation guards: pass.
• Independent review: 160-case base/head corpus, exactly 34 intended output changes (10 false standalone warnings removed, 12 mid-token openers and 12 mid-token closers preserve structural commas). Adjacent ordinary, unmatched, outside-credential, nested and newly merged initial/surname cases remain unchanged. 20,000 randomized tokenizer/splitter parity cases pass.
• Sibling-path sweep: StructuralCommaSplitter end-position tables and SuffixMapper already cast numeric keys; Text wrapped-token checks cast keys; NicknameMapper uses string matches/typed callbacks. No additional changes needed.

Local limitation: reused existing development dependencies in the cloud fallback; no fresh local Composer audit or PHP 8.3/8.5 execution. CI run 39680640552 passed all five expected jobs for exact head 29e6d578906573cb986ade9f6fe6abb37ffbfb36: PHP 8.3/8.4/8.5 each passed 1388 tests / 4012 assertions and Composer audit, plus static analysis and code style. No checks failed or skipped. No speed or memory improvement is claimed.