refactor: extract fix command utilities from src/index.ts to src/utils/fix-runner.ts (#437)

[AnupamKumar-1]

Closes #437

Summary

Moved three fix command utility functions from src/index.ts to a new dedicated module src/utils/fix-runner.ts.

What changed

• Created src/utils/fix-runner.ts with exported functions
• Moved buildFixCommandParts, runInstallCommand, commandLabelForPackageManager
• Updated src/index.ts to import from ./utils/fix-runner.js

Validation

• npm run build
• npm test — 326/326 tests passed

User-facing impact

• affect scanning behavior
• affect output formatting
• affect JSON output
• affect docs only

Notes

Pure refactor — no logic changes, no side effects.

[sonukapoor]

Thanks for the PR! #442 was opened for the same issue (#437) and does the same refactor with a couple of extra cleanups - it removes the now-unused SuggestedFixTarget and Finding imports from index.ts, and avoids the orphaned blank line at the top of the file where spawn was. We're going to go with that one. Would you mind closing this PR? Appreciate the contribution.