refactor: Implement simplified path handling system

[debugmcpdev]

Major path handling refactor to address cross-platform issues:

Key Changes:

• Replace complex PathValidator with SimpleFileChecker
• TRUE HANDS-OFF approach: accept all paths as-is from clients
• Container mode: simple /workspace/ prefix only
• Pass original paths to debug adapter unchanged
• Remove cross-platform path interpretation logic

New Components:

• src/utils/simple-file-checker.ts - minimal file existence checking
• Updated server.ts to use SimpleFileChecker for immediate UX feedback
• Enhanced documentation and architecture guides

Removed Components:

• src/utils/path-validator.ts - overly complex cross-platform logic
• Associated documentation for deprecated path resolution

Benefits:

• Eliminates unsolvable cross-platform edge cases
• Lets OS and debug adapter handle path resolution natively
• Cleaner, more maintainable codebase
• Better separation of concerns

This addresses Linux CI failures while maintaining Windows compatibility. Still investigating container test path resolution for 'host-examples' paths.

🤖 Generated with Claude Code

📋 Description

Please include a summary of the changes and which issue is fixed. Include relevant motivation and context.

Fixes # (issue number)

🔄 Type of Change

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• 🐛 Bug fix (non-breaking change which fixes an issue)
• ✨ New feature (non-breaking change which adds functionality)
• 💥 Breaking change (fix or feature that would cause existing functionality to not work as expected)
• 📚 Documentation update
• 🧹 Code refactoring
• ⚡ Performance improvement
• 🧪 Test improvement

✅ Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

🧪 Testing

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce.

# Example test command
npm test

Test Configuration:

• OS: [e.g., Ubuntu 22.04]
• Node version: [e.g., 20.11.0]
• Python version: [e.g., 3.11.5]

📸 Screenshots (if applicable)

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🔗 Related Issues

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• Related to #
• Depends on #
• Blocks #

📝 Additional Notes

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Reviewer: @debugmcp