2.1 Why Fitness Functions Matter

This is where most modular monolith examples fail.

Explain:

* architectural erosion

* accidental coupling

* dependency drift

* semantic leakage between modules

Then introduce:

* ArchUnitNET

* NetArchTest

* custom Roslyn analyzers (if any)

Use real examples from BrewUp.

This section can become a reference article on modular governance.