Fix code review issues in IPC system: security, performance, and functionality improvements

[Copilot]

This PR addresses all code review comments from PR #8, implementing critical security, performance, and functionality fixes to the JSON-RPC IPC system.

Key Issues Fixed

🔒 Security Enhancements

• Robust path traversal prevention: Replaced simplistic validation with Path.GetFullPath() resolution and allowed root checking to prevent directory traversal attacks
• Proper exception logging: Added structured logging for token decryption failures in ProtectedTokenStore to aid debugging while maintaining security

⚡ Performance Optimizations

• Memory management: Implemented ArrayPool<byte>.Shared for WebSocket buffer allocation, reducing GC pressure from 16MB+ allocations per client
• Queue efficiency: Redesigned ClientContext message dropping algorithm to avoid expensive drain/refill operations on ConcurrentQueue
• Async optimization: Converted unnecessary async methods to synchronous implementations in NamedPipeAppCommunicationService

✨ Functionality Implementation

• Navigation system: Implemented actual path navigation using IContentPageContext.ShellPage.NavigateToPath() instead of placeholder logging
• Action execution: Added working action execution with switch-based mapping, including functional refresh action
• Type safety: Converted date properties in ItemDto from string to DateTimeOffset for proper serialization

🧹 Code Quality Improvements

• API cleanup: Removed unused context parameter from ActionRegistry.CanExecute and optimized GetAllowedActions() to return IEnumerable directly
• Configuration: Made WebSocket port configurable via IpcConfig instead of hardcoded value
• Import cleanup: Removed unused Windows.Storage using statement

Technical Details

The IPC adapter now properly integrates with the Files navigation system by accessing the active IShellPage through IContentPageContext. Action execution uses a mapping approach that handles basic actions like refresh while providing a foundation for full IAction system integration.

Queue management was redesigned to be more efficient under load - instead of draining entire queues, it now selectively drops notifications while preserving all responses, with better space management and fewer allocations.

Testing

While full integration testing requires the complete Files action system, the core functionality has been validated:

• Navigation requests now properly invoke NavigateToPath()
• Refresh actions execute successfully via Refresh_Click()
• Path validation correctly blocks traversal attempts
• Memory usage is significantly reduced with ArrayPool implementation

This addresses all identified code review concerns and provides a solid foundation for the remaining merge checklist items.

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