Enhance docstrings across visualization module for improved clarity and consistency

[gearupsmile]

This PR updates and standardizes docstrings for nearly all functions in the viz.py module. The revised docstrings:

1. Clearly describe function purposes, parameters, and return types
2. Follow consistent formatting aligned with NumPy-style documentation
3. Improve code readability and maintainability for new contributors
4. Lay the groundwork for future automated documentation generation

No functionality or logic was altered. The changes are purely documentation-focused, ensuring smoother onboarding and better long-term maintainability.