refactor: move fix command utilities to separate module

[Kushaal-k]

Closes #437

Summary

Extracted fix command utility functions from src/index.ts into a dedicated utility module.

What changed

• Created src/utils/fix-runner.ts
• Moved fix command helper functions into the new module
• Updated src/index.ts to import the extracted utilities
• Removed unwanted imports from src/index.ts

Validation

• Ran npm run build
• Ran npm test
• Confirmed no behavior/output changes

Notes

This is a pure refactor with no intended behavior changes.

[sonukapoor]

Nice refactor - spawn moves to where it belongs and the orphaned imports are cleaned up too. One fix needed, plus a rebase before this can merge.