docs: Modernize diagrams

[gaureshpai]

Description

While reviewing the documentation, I found multiple diagrams were broken. This PR replaces these old ASCII art diagrams with modern text-based versions for better readability and maintenance across several documentation files.

Type of change

• Documentation update

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Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

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Pull Request Title

docs: Modernize diagrams

[nearlyforget]

Thanks for the contribution. The diagrams render well.