feat(services): enhance commit generation with tracing

- Added progress tracing for commit generation steps.
- Improved error handling when amending commits.
- Refactored commit service for better readability.

This update introduces progress tracing to enhance the commit generation
process. It improves error handling during commit amendments and refines
the service's structure for improved readability.

Co-Authored-By: Git Agent <noreply@git-agent.dev>

Author: xesrevinu