Update TestEditCommand to test the core editing functionality directly
using a Grok client instead of executing the full command. This makes
the test non-interactive and focuses on the editing logic. Also, adjust
the verification to trim whitespace before checking for the comment prefix.
- Introduced Makefile with targets for testing (all, coverage, agent-specific), building, installing, cleaning, and help
- Added unit and integration tests for agent command, edit command, and CleanCodeResponse function
- Refactored CleanCodeResponse to use regex for robust markdown fence removal in agent and client modules
- Ensured tests cover code cleaning, plan generation placeholders, and file editing functionality
