[Pybsama]

Fixes #27301

label-has-associated-control accepts empty label and association attributes because its root checks only test their presence. For example, <label aria-label="" htmlFor="name" /> and <label htmlFor="">Name</label> incorrectly pass.

Validate literal attribute values, share the labelling check between the root and descendants, and use JavaScript whitespace rules for label text. Association ids remain untrimmed, matching the upstream rule. Unknown dynamic values and spreads retain conservative handling.

Validation:

• The new regression test failed on current main before the fix.
• Both focused label-rule tests pass, including 40 new regression/control cases for root/nested attributes, falsy literals, settings aliases, custom label attributes, dynamic values, BOM/NEL whitespace and BigInt values.
• Independent AI code review completed; the Unicode whitespace finding was corrected and retested.
• Full post-commit just ready passed: 98 test targets, 5,061 passed / 161 ignored / 0 failed; formatting, code generation, checks, Clippy and documentation completed with a clean worktree.

AI-assisted with Codex.

[codspeed]

Merging this PR will not alter performance

✅ 5 untouched benchmarks
⏩ 91 skipped benchmarks¹

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_{Comparing Pybsama:codex/fix-label-attribute-values (1eb4e84) with main (7d381c3)}

Footnotes

1. 91 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. ↩