Prevent PigLatin crashes on empty whitespace tokens

[krotname]

Motivation

• Fix a crash in kyu5.PigLatin.pigIt where splitting on whitespace can produce empty tokens that reach substring(1)/charAt(0) and throw StringIndexOutOfBoundsException for empty input, leading spaces, or consecutive spaces.

Description

• Add an explicit empty-token guard in src/main/java/kyu5/PigLatin.java with if (w.isEmpty()) continue; before performing the Pig Latin transformation.
• Preserve existing behavior for punctuation by keeping the !w.matches("\\W") branch and appending punctuation tokens unchanged.
• Add a regression test handlesEmptyTokensWithoutThrowing in src/test/java/kyu5/PigLatinTest.java that covers empty input, leading whitespace, and consecutive whitespace.
• Commit message: Handle empty Pig Latin tokens safely.

Testing

• Ran mvn -q -Dtest=PigLatinTest test and the PigLatin test passed successfully.
• Ran mvn -q test and the full test suite passed successfully.
• Ran mvn -q verify and verification (including checks) completed successfully.
• Ran git diff --check and workspace status checks showed no issues.

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Codex Task

[krotname]

Superseded by the validated combined merge in #115: #115