DiscriminatorCollision
data class DiscriminatorCollision(val contract: String, val discriminator: String, val subtype: String) : Change
A sealed/polymorphic contract whose class discriminator key collides with a property of its subtype of the same name. Such a model is unserializable — kotlinx-serialization refuses to encode it — so, like a CoverageGap, it is a defect of a single snapshot surfaced on every diff (not a delta between two), letting the gate catch it statically before the first encode throws (#132).