Documentation: Adding documentation to the codebase for better code maintenance and contribution design.

[DevKiDCosmo]

A dedicated architecture.md would help newcomers understand the codebase more quickly, reducing onboarding time and enabling faster, more effective contributions.

[Evanev7]

Gonna link #930

[Evanev7]

I'll write this up soon anyway, thanks for raising the issue - it's good to know what's self-evident from the codebase and what isn't.