feat(cmd): support matrix require and option flags

[MeteorsLiu]

#113

[gemini-code-assist]

Code Review

This pull request refactors the matrix flag parsing logic to support --require and --option flags instead of the previous --matrix- prefix, and updates the corresponding unit tests. The review feedback points out a critical issue where specifying multiple --require or --option flags for the same key overwrites previous values instead of appending them, and provides suggestions to append the values to correctly support multi-value matrix dimensions.

[codecov]

Codecov Report

❌ Patch coverage is 87.50000% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 80.43%. Comparing base (927b834) to head (bfdbed1).

Files with missing lines	Patch %	Lines
cmd/llar/internal/matrix_flags.go	87.50%	3 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #114      +/-   ##
==========================================
- Coverage   80.47%   80.43%   -0.05%     
==========================================
  Files          37       37              
  Lines        2095     2116      +21     
==========================================
+ Hits         1686     1702      +16     
- Misses        297      300       +3     
- Partials      112      114       +2     

☔ View full report in Codecov by Sentry.
📢 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.

[fennoai]

Review Summary

Clean refactoring that replaces the --matrix- prefix approach with explicit --require and --option flags. Good test coverage and proper error handling. A few observations below — mostly around clarifying behavior and reducing duplication.

[luoliwoshang]

LGTM