[Bug]: @example transitive type check failure

### Describe the bug

https://github.com/microsoft/typespec/discussions/5835

Looks like transitive type check failed to check against source type

```
@example(#{
field: "foo",
})
model X {
field: string;
}

@example(#{
ref: "foo", <-- Failed to recognize X.field is of type string.
})
model Y {
ref: X.field;
}
```

### Reproduction

https://typespec.io/playground/?c=QGV4YW1wbGUoI3sKICBmaWVsZDogImZvbyIsCn0pCm1vZGVsIFggyx1zdHJpbmc7Cn0KCs49cmVm0jtZxTvFG1guxULEOg%3D%3D&e=%40typespec%2Fopenapi3&options=%7B%7D

### Checklist

- [x] Follow our [Code of Conduct](https://github.com/microsoft/typespec/blob/main/CODE_OF_CONDUCT.md)
- [x] Check that there isn't already an issue that request the same bug to avoid creating a duplicate.
- [x] Check that this is a concrete bug. For Q&A open a [GitHub Discussion](https://github.com/Microsoft/typespec/discussions).
- [x] The provided reproduction is a [minimal reproducible example](https://stackoverflow.com/help/minimal-reproducible-example) of the bug.