refactor(services): restructure commit flow

- Normalize and simplify error handling across commit flow
- Introduce explicit types and schemas for VCS diffs and hooks
- Centralize message generation and hook retry logic
- Update gitignore generation and network calls with safer error handling
- Align span names and logging attributes for telemetry

refactor of the services layer to streamline the commit flow, enhance
typings and schemas, and improve telemetry and error handling across
multiple files.

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

Author: xesrevinu