The invariant check system had grown into a single monolithic file pair containing 24 invariant checker classes. The large `InvariantCheck.cpp` file was a frequent source of merge conflicts and difficult to navigate. This refactoring improves maintainability and readability with zero behavioral changes.
In particular, this change:
- Splits `InvariantCheck.h` and `InvariantCheck.cpp` into 10 focused header/source pairs organized by domain under a new `invariants/` subdirectory.
- Extracts the shared `Privilege` enum and `hasPrivilege()` function into a dedicated `InvariantCheckPrivilege.h` header, so domain-specific files can reference them independently.
