[Enhancement]: Add integration tests for CLI #22

Problem

GCode lacks integration tests that verify the end-to-end functionality of the CLI tool. Unit tests only test individual functions in isolation, but do not ensure that the components work together correctly.

Proposed solution

Create integration tests that cover:

• CLI startup and argument parsing
• Model selection and switching
• Tool execution (bash, file operations, git)
• Session persistence and history
• Error handling and recovery
• Multi-turn conversations
• Ollama integration (if available)

Use a test framework like pytest with fixtures for temporary directories and mock API responses. Consider using tmux or pexpect for testing interactive CLI behavior.

Alternatives considered

• Manual testing only
• Using Docker for integration tests
• Creating a test harness script