[ShryukGrandhi]

Summary

• src/foo.test-utils.ts (and the .js/.mjs forms) is now classified as test support. Before this change it was scored as production code.
• utils counts as a scaffolding word only when a dot ties the name to a module (<module>.test-utils.*). Bare test-utils.js, which React and Preact publish as a package entry, is still production code.
• Added the issue's names to the corpus as regression rows, plus src/test-supporter.ts as a negative row.

On current main, foo.test-support.ts and foo.test-helpers.ts were already classified as support by _is_support_compound. Only foo.test-utils.ts was still unclassified, because utils is deliberately left out of _SUPPORT_NAME_WORDS. I kept these names out of test_infixes, so they are support and not tests. That matches how .test-harness. and .test-setup. are handled today.

Related Issues

Fixes #3269

Test Plan

• Tests pass (pytest): uv run pytest tests/unit/test_test_paths.py (the new foo.test-utils rows fail before the change and pass after it), plus every unit test module that references the test-path classifier (1725 passed)
• Lint passes (ruff check .) on the touched files

Checklist

• My code follows the project's code style
• I have added tests for new functionality
• All existing tests still pass
• I have updated documentation if needed

[RaghavChamadiya]

Requiring the dot that ties test-utils to a module keeps a bare test-utils.js counted as production. Thanks @ShryukGrandhi, and welcome.