Add one model host per provider and the unwrapping walk

app/MindWork AI Studio/Models/Hosting/Hosts/HostPerplexity.cs

@@ -0,0 +1,15 @@
+using AIStudio.Provider;
+
+namespace AIStudio.Models.Hosting.Hosts;
+
+/// <summary>
+/// Perplexity's own API.
+/// </summary>
+public sealed class HostPerplexity : ModelHost
+{
+    /// <inheritdoc />
+    public override LLMProviders Provider => LLMProviders.PERPLEXITY;
+
+    /// <inheritdoc />
+    public override ModelSource Source => new("https://docs.perplexity.ai/api-reference/chat-completions-post", new DateOnly(2026, 9, 11), "Models are named plainly, and there is one API to reach them through.");
+}