Update version from 8.5 to 8.6.0

- Update update_version.ps1 script to target 8.5→8.6.0
- Update package versions in all .csproj files
- Add Claude working files to .gitignore

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: claude