Version 3 design tests

using Agent.Core.Logging;using Agent.Core.Ollama;using Xunit;​namespace Agent.Core.DesignTests;​public class OllamaClientHistoryTests{    [Fact]    public void Save_and_load_conversation_round_trip()    {        string root = CreateTempHistoryRoot();        try        {            var logger = new Logger();            var client = new OllamaClient(logger, new ChatHistoryStore(root)) { Model = "gemma4" };​            client.ClearHistory();            client.History.Add("user", "Hello from design tests");            client.History.Add("assistant", "Hello back", tokens: 4);            client.SaveCurrentConversation();​            client.StartNewSession();            client.ClearHistory();            Assert.DoesNotContain(                client.History,                m => !m.Role.Equals("system", StringComparison.OrdinalIgnoreCase));​            IReadOnlyList<ChatSessionSummary> sessions = client.ListSavedConversations();            Assert.Single(sessions);​            Assert.True(client.LoadSavedConversation(1));            Assert.Contains(client.History, m => m.Content.Contains("Hello from design tests", StringComparison.Ordinal));            Assert.Contains(client.History, m => m.Content.Contains("Hello back", StringComparison.Ordinal));        }        finally        {            TryDeleteDirectory(root);        }    }​    [Fact]    public void LoadSavedConversation_returns_false_for_invalid_index()    {        string root = CreateTempHistoryRoot();        try        {            var client = new OllamaClient(new Logger(), new ChatHistoryStore(root));            Assert.False(client.LoadSavedConversation(99));        }        finally        {            TryDeleteDirectory(root);        }    }​    private static string CreateTempHistoryRoot()    {        string path = Path.Combine(Path.GetTempPath(), "AgentCore-DesignTests", Guid.NewGuid().ToString("N"));        Directory.CreateDirectory(path);        return path;    }​    private static void TryDeleteDirectory(string path)    {        try        {            if (Directory.Exists(path))            {                Directory.Delete(path, recursive: true);            }        }        catch        {        }    }}​