refactor: remove dead code and add 100% test branch coverage

[remarkablemark]

What is the motivation for this pull request?

Refactor to remove dead code and achieve 100% test branch coverage.

What is the current behavior?

• comments() had an unreachable if (c !== false) guard — comment() never returns false
• declarations() had an unreachable if (decl !== false) guard — declaration() never returns false
• comments() had an unreachable rules = rules || [] fallback — it is always called with a rules array argument
• trim() falsy branch was untested — no test covered a declaration whose value is entirely a CSS comment

Branch coverage was 89.18%.

What is the new behavior?

• Removed three dead code branches from index.js
• Added snapshot test case 'parses declaration with comment-only value' (e.g. color: /* red */;) to cover the trim('') branch

Branch coverage is now 100%.

Checklist:

• Conventional Commits
• Tests
• Documentation

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (1d9d45c) to head (37f5d35).

Additional details and impacted files

@@            Coverage Diff            @@
##            master      #553   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            1         1           
  Lines          103       100    -3     
  Branches        20        17    -3     
=========================================
- Hits           103       100    -3     

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[mergify]

Tick the box to add this pull request to the merge queue (same as @mergifyio queue).

• Queue this pull request