Add Luna.Core server with SignalR hub, session management, and tool system

Implement the core application server as an ASP.NET web host with:
- SignalR ChatHub for real-time client communication
- Session management with token estimation for context windowing
- Extensible tool system with attribute-based tool discovery
- Chat stream update builder for streaming AI responses
- App configuration with appsettings for development and production

Luna.Core/Tools/BuiltIn/CoreTools.cs

@@ -0,0 +1,24 @@
+namespace Luna.Core.Tools.BuiltIn;
+
+public class CoreTools : IToolbox
+{
+    public string Name => "core";
+
+    public record Channel(string Name, string Health, bool IsConnected);
+    public record ListChannelsResult(IEnumerable<Channel> Channels);
+    
+    [Tool("list_channels", "List available communication channels")]
+    public ListChannelsResult ListChannels()
+    {
+        return new ListChannelsResult([
+            new Channel("cli", "healthy", true),
+            new Channel("web", "healthy", false),
+            new Channel("telegram", "healthy", false)
+        ]);
+    }
+    
+    [Tool("change_channel", "Change the active communication channel")]
+    public void ChangeChannel(string channelName)
+    {
+    }
+}

Luna.Core/Tools/Extensions/ServiceCollectionExtensions.cs

@@ -0,0 +1,19 @@
+namespace Luna.Core.Tools.Extensions;
+
+public static class ServiceCollectionExtensions
+{
+    extension(IServiceCollection services)
+    {
+        public IServiceCollection AddTools()
+        {
+            services.AddSingleton<IToolsProvider, ToolsProvider>();
+            
+            typeof(ToolsProvider).Assembly.GetTypes()
+                .Where(t => typeof(IToolbox).IsAssignableFrom(t) && !t.IsInterface && !t.IsAbstract)
+                .ToList()
+                .ForEach(t => services.AddTransient(typeof(IToolbox), t));
+            
+            return services;
+        }
+    }
+}

Luna.Core/Tools/IToolbox.cs

@@ -0,0 +1,30 @@
+using System.Reflection;
+using Microsoft.Extensions.AI;
+
+namespace Luna.Core.Tools;
+
+public interface IToolbox
+{
+    public string Name { get; }
+    
+    public sealed IEnumerable<AITool> GetTools()
+    {
+        var type = GetType();
+
+        List<(ToolAttribute Attribute, MethodInfo Method)> tools = [];
+        foreach (var method in type.GetMethods(BindingFlags.Public | BindingFlags.Instance))
+        {
+            var attribute = method.GetCustomAttribute<ToolAttribute>();
+            if (attribute is null) continue;
+            
+            tools.Add((attribute, method));
+        }
+        
+        return tools.Select(tool => AIFunctionFactory.Create(
+            tool.Method,
+            this,
+            $"{this.Name}/{tool.Attribute.Name}",
+            tool.Attribute.Description
+        ));
+    }
+}

Luna.Core/Tools/IToolsProvider.cs

@@ -0,0 +1,8 @@
+using Microsoft.Extensions.AI;
+
+namespace Luna.Core.Tools;
+
+public interface IToolsProvider
+{
+    IEnumerable<AITool> GetTools();
+}

Luna.Core/Tools/ToolAttribute.cs

@@ -0,0 +1,8 @@
+namespace Luna.Core.Tools;
+
+[AttributeUsage(AttributeTargets.Method)]
+public class ToolAttribute(string name, string description) : Attribute
+{
+    public string Name { get; } = name;
+    public string Description { get; } = description;
+}

Luna.Core/Tools/ToolsProvider.cs

@@ -0,0 +1,9 @@
+using Microsoft.Extensions.AI;
+
+namespace Luna.Core.Tools;
+
+public sealed class ToolsProvider(IEnumerable<IToolbox> toolboxes) : IToolsProvider
+{
+    public IEnumerable<AITool> GetTools()
+        => toolboxes.SelectMany(t => t.GetTools());
+}