fix(linter/jest/prefer-lowercase-title): false positive when lowercaseFirstCharacterOnly is false

[connorshea]

With lowercaseFirstCharacterOnly: false, the char-scanning loop in lint_string never took its early return: the chars().nth(n) lookup inside the loop cannot fail for n < chars().count(), so the else { return } branch was unreachable. As a result, all-lowercase titles fell through the loop and were reported as violations.

This replaces the loop with a bytes().any(|b| b.is_ascii_uppercase()) check (uppercase detection here is inherently ASCII: the rule's fix path lowercases via ASCII) and adds two regression pass-tests to vitest/prefer-lowercase-title covering all-lowercase titles under lowercaseFirstCharacterOnly: false.

The old loop was also accidentally quadratic (chars().nth(n) per iteration restarts the char walk each time).

Benchmark

Interleaved paired-sample benchmark (N=40) on a synthetic title-dense fixture, single-rule oxlintrc (titles crafted to report on both binaries so the perf comparison is apples-to-apples despite the behavior fix):

	mean
before	15.70 ms
after	7.60 ms

2.07× faster (paired t=44). Parse-only differential was null.

Disclosure

This change was implemented and benchmarked with AI assistance (Claude Code), and has been reviewed by the submitter.

🤖 Generated with Claude Code

[codspeed-hq]

Merging this PR will not alter performance

✅ 5 untouched benchmarks
⏩ 66 skipped benchmarks¹

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_{Comparing fix/linter-prefer-lowercase-title (94cdb53) with main (8a4f028)}

Footnotes

1. 66 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

[camc314]

nice!