CycleDetector

Detects guaranteed-infinite mapping cycles at compile time.

An edge is only included in cycle detection when it traverses a field that is:

• non-nullable (so the value MUST exist — nullable is always break-able at runtime)

• not a collection (a collection can be empty, so recursion terminates)

Examples:

• A -> B -> A through non-null fields → ERROR (cycle)

• Cat(parent: Cat?) → OK (nullable breaks the cycle)

• Node(children: List<Node>) → OK (collection breaks the cycle)