test: match .gitattributes rules as whole lines in the drift guard

[HasselNot7]

Description

Follow-up to #555, implementing @cevheri's review suggestion. The drift guard used toContain(...), which also matches a commented-out rule (# * text=auto eol=lf), so it wasn't really guarding the line. This anchors each rule to a whole line with a multiline regex, so a commented-out or altered rule fails the check.

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Code refactoring
• Performance improvement
• Test addition or update

Related Issue

Follow-up to #555 (suggestion: #555 (comment)). Does not close an issue on its own.

Changes Made

• tests/unit/gitattributes.test.ts: replace the two toContain assertions with a whole-line match (^rule$ with the m flag; literals are regex-escaped). The same anchoring is applied to the four #114 patterns.

Testing

• I have tested this locally

• I have added/updated tests

• bun test tests/unit/gitattributes.test.ts on this branch: 2 pass / 0 fail.

• Confirmed the guard now fails when the rule is commented out as # * text=auto eol=lf (the old toContain passed in that case), then restored the file.

• eslint clean on the changed file.

Screenshots (if applicable)

n/a (test-only change).

Checklist

• My code follows the project's code style guidelines
• I have performed a self-review of my code
• My changes generate no new warnings
• I have added tests that prove the guard is effective
• Test-only change; no runtime code is touched

Additional Notes

Implements the maintainer's own optional follow-up from #555. AI-assisted (agent drafted the change; verified manually with the comment-out check above).

[cevheri]

Merged, thank you. Checked it the way you described: with the rule commented out the new guard fails while the old toContain version still passed, so this closed a real gap.