Classify embedding failures at the provider level

app/MindWork AI Studio/Provider/Perplexity/ProviderPerplexity.cs

@@ -77,7 +77,7 @@ public sealed class ProviderPerplexity() : BaseProvider(LLMProviders.PERPLEXITY,
     /// <inhertidoc />
     public override Task<IReadOnlyList<IReadOnlyList<float>>> EmbedTextAsync(Model embeddingModel, SettingsManager settingsManager, CancellationToken token = default, params List<string> texts)
     {
-        return Task.FromResult<IReadOnlyList<IReadOnlyList<float>>>([]);
+        throw this.CreateEmbeddingsNotSupportedException();
     }
 
     /// <inheritdoc />