request: sample to get return value of eval

can you add sample to get return value of eval() ?

something like this:
```
val result : ResultWithDiagnostics = eval(...)

result.castOrError> {
"script evaluation failed. $it"
}.value.returnValue.castOrError {
"script evaluation result is $it"
}.value.castOrError { // your expected class for value
"script returns value, but it's not AppConfig. ${it?.javaClass?.simpleName}"
}.let { config = it }

inline fun Any?.castOrError(noinline messageCreator:(Any?)->String) =
(this as? T) ?: error(messageCreator(this))
```

Start by locating the repository's existing Kotlin script examples and the eval() usage. Add a sample showing how to retrieve and type-check an evaluation return value using the requested ResultWithDiagnostics flow, then verify that the example is consistent with the repository's existing examples.

Written by the indexing model from the issue text.