Added the exact token count where the provider reports it

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

app/MindWork AI Studio/Provider/OpenAI/ChatCompletionUsage.cs

@@ -0,0 +1,30 @@
+// ReSharper disable ClassNeverInstantiated.Global
+namespace AIStudio.Provider.OpenAI;
+
+/// <summary>
+/// What an OpenAI-compatible provider reports a chat completion cost.
+/// </summary>
+/// <remarks>
+/// Every number is optional because this is somebody else's JSON: the block arrives only when the
+/// request asked for it, and the providers which follow the shape loosely leave fields out. Reading
+/// it is one thing, believing it another -- <see cref="TokenUsage.OfReported"/> decides that.
+/// </remarks>
+public sealed record ChatCompletionUsage
+{
+    /// <summary>
+    /// What everything sent to the model cost.
+    /// </summary>
+    public int? PromptTokens { get; init; }
+
+    /// <summary>
+    /// What the model wrote in answer.
+    /// </summary>
+    public int? CompletionTokens { get; init; }
+
+    /// <summary>
+    /// What the provider says both of them add up to. Read but not relied upon: it is the sum of
+    /// the other two wherever a provider fills all three, and this way a provider which sends only
+    /// this one is not a reason to throw the other numbers away.
+    /// </summary>
+    public int? TotalTokens { get; init; }
+}