fix(ai): request structured JSON for queued strategies

JobTrackerApi.Tests/CvAiEvaluationTests.cs

@@ -71,6 +71,22 @@ public sealed class CvAiEvaluationTests
         Assert.Null(await service.GenerateSectionWithMetadataAsync("Improve", "Source", AiGenerationOutputMode.CvBlocksJson));
     }
 
+    [Fact]
+    public async Task Structured_generation_has_an_explicit_mode_and_cannot_reuse_text_cache()
+    {
+        var handler = new CaptureHandler();
+        var factory = new Mock<IHttpClientFactory>();
+        factory.Setup(value => value.CreateClient("ai-service")).Returns(new HttpClient(handler) { BaseAddress = new Uri("http://localhost") });
+        using var cache = new MemoryCache(new MemoryCacheOptions());
+        var service = new SummarizerService(factory.Object, cache);
+        await service.GenerateSectionWithMetadataAsync("Return JSON.", "Fictional source.");
+        Assert.NotNull(await service.GenerateSectionWithMetadataAsync("Return JSON.", "Fictional source.", AiGenerationOutputMode.StructuredJson));
+        Assert.Equal(2, handler.RequestCount);
+        using var body = JsonDocument.Parse(handler.Body!);
+        Assert.Equal("structured_json", body.RootElement.GetProperty("output_mode").GetString());
+        Assert.Null(await ((ISummarizerService)new OlderSummarizer()).GenerateSectionWithMetadataAsync("Return JSON.", "Source", AiGenerationOutputMode.StructuredJson));
+    }
+
     private sealed class CaptureHandler : HttpMessageHandler
     {
         public string? Path { get; private set; }