Regression: debug mode causes passing test to fail

### Expected Behavior

Test that pass in normal mode also pass in debug mode

### Actual Behaviour

After upgrading Micronaut from 4.7.6 to 4.8.2 running a test in debug mode fails with SerdeException: No serializable introspection present for type OnAssemblyException

### Steps To Reproduce

Add suspend method in controller that throws a Problem. Call that endpoint in a test and run test in Debug mode. A different response is given depending if tests are run in debug or normal mode.

```Kotlin
@Get
@Produces(MediaType.APPLICATION_JSON_PROBLEM)
open suspend fun index(): String {
throw Problem.builder().withTitle("Validation errors").withStatus(HttpStatusType(HttpStatus.BAD_REQUEST)).build()
}
```

### Environment Information

M1 MacOS 15.5
Java 21
Intellij IdeaIntelliJ IDEA 2025.1.1.1 (Ultimate Edition) Build #IU-251.25410.129, built on May 9, 2025 Kotlin: 251.25410.129-IJ

### Example Application

https://github.com/erkieh/micronaut-debug-error

### Version

4.8.3-SNAPSHOT

Start with the example application at github.com/erkieh/micronaut-debug-error and the suspend controller endpoint shown in the issue. Reproduce the request in normal and IntelliJ debug modes on the stated environment, then trace the SerdeException involving OnAssemblyException; done means the endpoint returns the same response in both modes.

Written by the indexing model from the issue text.