feat(Mountain): Enhance workspace RPC handlers with improved URI handling and error reporting

- Refactored `file_path_to_uri_components_dto` to handle edge cases in path conversion, ensuring VS Code-compatible URI DTOs with proper escaping and fallback mechanisms
- Improved error reporting in workspace folder handlers with contextual lock errors (`format_workspace_app_state_lock_error_for_rpc`) and structured error codes
- Enhanced `findFiles` implementation with robust glob pattern resolution respecting base URIs and security checks against folder boundaries
- Added detailed documentation for RPC handler contracts and notification workflows between Mountain and Cocoon
- Implemented proper workspace trust state management foundations with atomic bool operations
- Updated directory walking logic to use `ignore` crate capabilities for `.gitignore` handling and symlink resolution

These changes improve compatibility with VS Code extension requirements while maintaining security boundaries, crucial for Cocoon's extension host operations in the Land architecture.

Author: NikolaRHristov