Update evaluate_task.py

[r0cketdyne]

Here's why I made the refinements:

Consolidated Imports: I grouped the import statements to improve readability and maintainability. It's a standard practice in Python to consolidate imports for better organization.

Simplified File Backup Function: Simplified the _backup_existing function by removing unnecessary conditions and making the logic clearer. This makes the code easier to understand and maintain.

Improved JSON Export Functions: Refactored the _export_json_task and related functions to streamline the code. This makes it more concise and easier to follow by reducing redundancy and improving readability.

Enhanced Result Sanitization: Updated the _sanitize_results function to handle non-float values more gracefully by printing a warning instead of raising an error. This ensures that the code can handle unexpected data types without crashing.

Streamlined Model Validation: Improved the validation of model names to ensure that invalid model names are properly handled and reported. This enhances the robustness of the code by preventing potential errors due to invalid inputs.

Enhanced Command-Line Output: Adjusted the output messages to provide more informative feedback, such as indicating the presence of a proxy socket and reporting errors with invalid model names. This improves the user experience by providing clearer guidance and feedback.