Bump actions/checkout from v4 to v6 in /.github/workflows

[UltralyticsAssistant]

Bump actions/checkout from v4 to v6 in /.github/workflows

This PR updates GitHub Actions references in this repository.

Examples:

• Branch: actions/checkout@main stays on @main
• Major tag: actions/checkout@v4 updates to @v5
• Specific tag: astral-sh/setup-uv@v0.5.0 updates to @v0.9.4
• SHA pinned: actions/checkout@<sha> # v4.1.0 updates to the latest release SHA and tag comment

_{Made with ❤️ by Ultralytics Actions}

🛠️ PR Summary

_{Made with ❤️ by Ultralytics Actions}

🌟 Summary

This PR modernizes the repo’s GitHub Actions and Python type hints, improving maintainability and keeping the Replicate predictors up to date 🚀

📊 Key Changes

• Updated GitHub Actions checkout steps from actions/checkout@v4 to actions/checkout@v6 in both CI and push workflows ⚙️
• Replaced typing.Optional imports with from __future__ import annotations in predictor files for:
  • yolo11n
  • yoloe11s
  • yolov8s-worldv2
• Simplified output type annotations from Optional[Path] and Optional[str] to modern Path | None and str | None ✨
• No model logic or prediction behavior was changed; updates are focused on code style and workflow maintenance ✅

🎯 Purpose & Impact

• Keeps automation workflows aligned with newer GitHub Actions versions, which can help with long-term CI reliability and compatibility 🔄
• Modernizes Python code to use cleaner, more readable type hints, making the predictor files easier to maintain 🧹
• Reduces technical debt without affecting how users run or consume these Replicate models 🤝
• Low-risk update overall: developers benefit from cleaner infrastructure and code, while end users should see no functional changes 📦