feat: list available Copilot models on startup

- After successful CopilotClient.StartAsync, call ListModelsAsync and emit 'ocp: models: ...' line (before HTTP server listens)
- Add small pure ToStartupModelsLine formatter in OpenAIMapper (reuses ToModelsListResponse shape for consistency)
- Unit tests for the startup formatter with real ModelInfo instances
- Primary entrypoint (ocp.exe / dotnet run) now produces the model list on startup

Author: kzu

src/Tests/OpenAIMapperTests.cs

@@ -64,4 +64,24 @@ public void Roundtrip_ChatRequest_SerializesAsExpected()
         Assert.Contains("\"role\":\"user\"", json);
         Assert.Contains("test prompt", json);
     }
+
+    [Fact]
+    public void ToStartupModelsLine_ProducesOcpPrefixedIdsLine_UsingMapperShape()
+    {
+        // ModelInfo has public ctor (verified via reflection); properties are writable
+        var models = new List<ModelInfo>
+        {
+            new ModelInfo { Id = "gpt-5" },
+            new ModelInfo { Id = "claude-sonnet-4.5" }
+        };
+        var line = OpenAIMapper.ToStartupModelsLine(models);
+        Assert.Equal("ocp: models: gpt-5, claude-sonnet-4.5", line);
+    }
+
+    [Fact]
+    public void ToStartupModelsLine_HandlesEmptyList()
+    {
+        var line = OpenAIMapper.ToStartupModelsLine(new List<ModelInfo>());
+        Assert.Equal("ocp: models: ", line);
+    }
 }

src/ocp/OpenAIMapper.cs

@@ -31,6 +31,17 @@ public static ModelsListResponse ToModelsListResponse(IList<ModelInfo> models)
         var data = models.Select(m => new ModelObject(m.Id, "model", now, "copilot")).ToList();
         return new ModelsListResponse("list", data);
     }
+
+    /// <summary>
+    /// Pure formatter for startup console output. Returns a single "ocp: models: ..." line.
+    /// Reuses ToModelsListResponse shape internally for consistency.
+    /// </summary>
+    public static string ToStartupModelsLine(IList<ModelInfo> models)
+    {
+        var resp = ToModelsListResponse(models);
+        var ids = resp.Data.Select(d => d.Id);
+        return "ocp: models: " + string.Join(", ", ids);
+    }
 }
 
 // OpenAI compatible request/response shapes (minimal, for /v1 compat)

src/ocp/Program.cs

@@ -83,6 +83,8 @@
 {
     await client.StartAsync();
     Console.WriteLine("ocp: Copilot client started.");
+    var models = await client.ListModelsAsync();
+    Console.WriteLine(OpenAIMapper.ToStartupModelsLine(models));
 }
 catch (Exception ex)
 {