Add named CLI arguments while maintaining backwards compatibility with positional arguments

[nicolasbisurgi]

Description

Introduces a proper argument parser using Python's argparse module with named arguments, while maintaining full backwards compatibility with the existing positional argument style.

New named argument style:

python rushti.py --tasks tasks.txt --workers 4 --mode opt --retries 2 --result results.csv
# Or with short flags:
python rushti.py -t tasks.txt -w 4 -m opt -r 2 -o results.csv

Backwards compatibility: The existing positional style continues to work exactly as before:

python rushti.py tasks.txt 4 opt 2 results.csv

Implementation approach (detection-based hybrid):

• If any named argument (starting with -) is detected, use the new argparse-based parser
• Otherwise, fall back to the existing positional argument parsing logic

This provides:

• Full backwards compatibility for existing scripts and automation
• Improved UX with --help support and meaningful argument names
• Flexibility to specify only the arguments you need (e.g., --retries 3 without specifying --mode)
• A clear migration path for users who want to adopt the new style

Closes #105

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update
• Code refactoring
• CI/CD or build changes

Release Label

Suggested: release:minor - New feature (named arguments), non-breaking change

Checklist

• I have tested my changes locally
• I have updated documentation if needed
• My code follows the project's coding style
• I have added tests if applicable

[nicolasbisurgi]

@MariusWirtz - I think this is a prerequisite for #104 as we would need a --run-exclusive argument to prevent other instance of RushTI to run in parallel.