Fix Unicode case expansion in AdjustCase

[krotname]

Motivation

• Repair a Unicode correctness regression in adjustCaseToLower where lowercasing the whole string first could produce multi-code-point expansions (e.g. U+0130 → i + combining dot) and leave the combining mark in the suffix.

Description

• Change the order of operations to separate the original first UTF-16 unit and then lowercase the remainder with string.substring(1).toLowerCase(Locale.ROOT) to avoid retaining extra code points produced by the first character's case mapping.
• Preserve the original behavior of uppercasing the first unit via string.substring(0, 1).toUpperCase(Locale.ROOT) and concatenating it with the lowercased suffix.
• Add a focused regression test adjustsSuffixWithoutRetainingExpandedLowercaseCharacters that asserts other.AdjustCase.adjustCaseToLower("\u0130BC") yields "\u0130bc".

Testing

• Ran mvn -Dtest=AdjustCaseTest test and the test suite containing the new regression test completed successfully (Tests run: 2, Failures: 0).
• Ran git diff --check and git status to ensure no whitespace or repository issues and a clean working tree.
• The change is limited and unit-tested to prevent reintroduction of the combining-character regression.

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Codex Task

[chatgpt-codex-connector]

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[krotname]

Закрываю как superseded by #116: изменения перенесены в одну проверенную ветку, все review findings учтены; локальный mvn verify прошёл полностью.