Add directory hierarchy awareness to document sorting

[MuhammadTalha57]

🤔 What's changed?

This PR updates the document sorting logic so nested directories are ordered before direct child files, matching how users typically expect hierarchy-aware sorting to behave in IDEs and file explorers.

⚡️ What's your motivation?

Addresses issue #492

🏷️ What kind of change is this?

• 🏦 Refactoring/debt/DX (improvement to code design, tooling, etc. without changing behaviour)

♻️ Anything particular you want feedback on?

I’d especially appreciate feedback on the test coverage I added. I couldn’t find a more appropriate place for these tests, so I added them in the samples folder, which also appears to be how the previous implementation was covered.

📋 Checklist:

• I agree to respect and uphold the Cucumber Community Code of Conduct
• I've changed the behaviour of the code
  • I have added/updated tests to cover my changes.
• My change requires a change to the documentation.
  • I have updated the documentation accordingly.
• Users should know about my change
  • I have added an entry to the "Unreleased" section of the CHANGELOG, linking to this pull request.

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