v3.0.0

Added

• @studnicky/no-readonly-in-data-type ESLint rule (autofixable, type-checker driven): forbids readonly modifiers baked into exported type alias data definitions. Detection is proven through the type system with no name matching — generic transformation types (mapped types like DeepReadonlyType, conditional types like DeepMergeType) resolve to types with no concrete readonly members and are never flagged, and a type that merely references a readonly type is left alone. The fix removes the readonly modifiers.

Changed

• Breaking: Exported data type aliases across the toolkit no longer carry readonly modifiers. A type describes shape, not access policy; consumers declare immutability at the use site (readonly, Readonly<T>, DeepReadonlyType<T>). This includes @studnicky/types JsonValueType and the *Type option/result shapes across the primitives. interface contracts and all use-site readonly (parameters, class fields, Readonly<T> references) are unchanged.
• Breaking: @studnicky/fetch replaces the request/response interceptor mechanism with protected override lifecycle hooks. Subclass FetchClient and override onRequest(context) / onResponse(context) to transform the outgoing request or incoming response. Removed: the requestInterceptor/responseInterceptor config fields and builder methods, InterceptorManager, and the RequestInterceptorType/ResponseInterceptorType exports; the context types are now RequestContextType / ResponseContextType. The package no longer depends on @studnicky/pipeline.
• @studnicky/interface-must-be-contract is now type-checker driven and autofixable. It resolves each member's type through the checker and flags an interface only when every member is JSON-serializable — including generic type-parameter bodies such as interface Box<T> { v: T }. The fix rewrites a data-shape interface to a type alias, preserving export/declare modifiers, generics, and extends (as an intersection), and is skipped for declaration-merged or globally-augmented interfaces.