kotlin-code-authoringlisted

# Kotlin code authoring Write Kotlin that matches the target repository's compiler version, formatter, existing style, and framework conventions. Inspect nearby Kotlin code and project instructions before choosing an API or style. ## Construction baseline Apply the same Kotlin/Spring principles used by `kotlin-spring-review` before writing code. It is an installed dependency: read its [principles](../kotlin-spring-review/reference/principles.md) and route only the relevant topics through its [KB index](../kotlin-spring-review/reference/kb/INDEX.md). Use those references as construction constraints, not as a request to produce a review. - Preserve the repository's layer and dependency direction. Do not bypass the designated application/service boundary or leak persistence types across a boundary when local architecture rules prohibit it. - Prefer `val`, explicit null handling, read-only public collection types, and `data`/`sealed` types where their semantics fit. Do not introduce `!!`, unsafe casts, or mutable public state merely to shorten an implementation. - For Spring-managed mandatory dependencies, use constructor injection. Put transaction behavior at the existing application/service boundary; preserve proxy and transaction conventions instead of adding broad annotations speculatively. - Validate and translate errors at the repository's existing boundary. Do not swallow broad exceptions or invent error contracts. - When behavior changes, create or update a focused te