Expected 'app.bsky.embed.images' or 'app.bsky.embed.external' or 'app.bsky.embed.record' or 'app.bsky.embed.recordWithMedia' but found 'AppBskyEmbedImages.Main'.

First: thanks for your works! Love there is a Kotlin codebase for Bluesky already
Prefixing this issue: I extracted the API from your codebase to experiment with a bot.
For getTimeline calls with a certain cursor I am seeing this:

```
com.squareup.moshi.JsonDataException: Expected 'app.bsky.embed.images' or 'app.bsky.embed.external' or 'app.bsky.embed.record' or 'app.bsky.embed.recordWithMedia' but found 'AppBskyEmbedImages.Main'.
at io.github.akiomik.seiun.api.adapters.Union4JsonAdapter.determineEither(Union4JsonAdapter.kt:99)
at io.github.akiomik.seiun.api.adapters.Union4JsonAdapter.fromJson(Union4JsonAdapter.kt:61)
at io.github.akiomik.seiun.api.adapters.Union4JsonAdapter.fromJson(Union4JsonAdapter.kt:15)
at com.squareup.moshi.internal.NullSafeJsonAdapter.fromJson(NullSafeJsonAdapter.java:41)
at com.squareup.moshi.kotlin.reflect.KotlinJsonAdapter.fromJson(KotlinJsonAdapter.kt:86)
at com.squareup.moshi.internal.NullSafeJsonAdapter.fromJson(NullSafeJsonAdapter.java:41)
at com.squareup.moshi.adapters.PolymorphicJsonAdapterFactory$PolymorphicJsonAdapter.fromJson(PolymorphicJsonAdapterFactory.java:264)
at com.squareup.moshi.internal.NullSafeJsonAdapter.fromJson(NullSafeJsonAdapter.java:41)
at com.squareup.moshi.kotlin.reflect.KotlinJsonAdapter.fromJson(KotlinJsonAdapter.kt:86)
at com.squareup.moshi.internal.NullSafeJsonAdapter.fromJson(NullSafeJsonAdapter.java:41)
at com.squareup.moshi.kotlin.reflect.KotlinJsonAdapter.fromJson(KotlinJsonAdapter.kt:86)
at com.squareup.moshi.internal.NullSafeJsonAdapter.fromJson(NullSafeJsonAdapter.java:41)
at com.squareup.moshi.CollectionJsonAdapter.fromJson(CollectionJsonAdapter.java:81)
at com.squareup.moshi.CollectionJsonAdapter$2.fromJson(CollectionJsonAdapter.java:55)
at com.squareup.moshi.internal.NullSafeJsonAdapter.fromJson(NullSafeJsonAdapter.java:41)
at com.squareup.moshi.kotlin.reflect.KotlinJsonAdapter.fromJson(KotlinJsonAdapter.kt:86)
at com.squareup.moshi.internal.NullSafeJsonAdapter.fromJson(NullSafeJsonAdapter.java:41)
at retrofit2.converter.moshi.MoshiResponseBodyConverter.convert(MoshiResponseBodyConverter.java:46)
at retrofit2.converter.moshi.MoshiResponseBodyConverter.convert(MoshiResponseBodyConverter.java:27)
at com.slack.eithernet.ApiResultConverterFactory$ApiResultConverter.convert(ApiResult.kt:230)
at com.slack.eithernet.ApiResultConverterFactory$ApiResultConverter.convert(ApiResult.kt:226)
at retrofit2.OkHttpCall.parseResponse(OkHttpCall.java:243)
at retrofit2.OkHttpCall$1.onResponse(OkHttpCall.java:153)
at okhttp3.internal.connection.RealCall$AsyncCall.run(RealCall.kt:519)
at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
at java.base/java.lang.Thread.run(Thread.java:829)
```

Very likely your android app will also stumble over this content.
Also wonder if you would be open to extracting the API to a separate project (I could also PR this)