Implement InMemory Transport Layer for StellaOps Router

- Added InMemoryTransportOptions class for configuration settings including timeouts and latency.
- Developed InMemoryTransportServer class to handle connections, frame processing, and event management.
- Created ServiceCollectionExtensions for easy registration of InMemory transport services.
- Established project structure and dependencies for InMemory transport library.
- Implemented comprehensive unit tests for endpoint discovery, connection management, request/response flow, and streaming capabilities.
- Ensured proper handling of cancellation, heartbeat, and hello frames within the transport layer.

tests/StellaOps.Router.Transport.InMemory.Tests/InMemoryConnectionRegistryTests.cs

@@ -0,0 +1,106 @@
+using StellaOps.Router.Transport.InMemory;
+using Xunit;
+
+namespace StellaOps.Router.Transport.InMemory.Tests;
+
+public class InMemoryConnectionRegistryTests
+{
+    [Fact]
+    public void CreateChannel_CreatesNewChannel()
+    {
+        // Arrange
+        using var registry = new InMemoryConnectionRegistry();
+
+        // Act
+        var channel = registry.CreateChannel("conn-1");
+
+        // Assert
+        Assert.NotNull(channel);
+        Assert.Equal("conn-1", channel.ConnectionId);
+        Assert.Equal(1, registry.Count);
+    }
+
+    [Fact]
+    public void CreateChannel_ThrowsIfDuplicate()
+    {
+        // Arrange
+        using var registry = new InMemoryConnectionRegistry();
+        registry.CreateChannel("conn-1");
+
+        // Act & Assert
+        Assert.Throws<InvalidOperationException>(() => registry.CreateChannel("conn-1"));
+    }
+
+    [Fact]
+    public void GetChannel_ReturnsNullForUnknown()
+    {
+        // Arrange
+        using var registry = new InMemoryConnectionRegistry();
+
+        // Act
+        var channel = registry.GetChannel("unknown");
+
+        // Assert
+        Assert.Null(channel);
+    }
+
+    [Fact]
+    public void GetChannel_ReturnsExistingChannel()
+    {
+        // Arrange
+        using var registry = new InMemoryConnectionRegistry();
+        var created = registry.CreateChannel("conn-1");
+
+        // Act
+        var retrieved = registry.GetChannel("conn-1");
+
+        // Assert
+        Assert.Same(created, retrieved);
+    }
+
+    [Fact]
+    public void RemoveChannel_RemovesAndDisposes()
+    {
+        // Arrange
+        using var registry = new InMemoryConnectionRegistry();
+        var channel = registry.CreateChannel("conn-1");
+
+        // Act
+        var removed = registry.RemoveChannel("conn-1");
+
+        // Assert
+        Assert.True(removed);
+        Assert.Equal(0, registry.Count);
+        Assert.True(channel.LifetimeToken.IsCancellationRequested);
+    }
+
+    [Fact]
+    public void RemoveChannel_ReturnsFalseForUnknown()
+    {
+        // Arrange
+        using var registry = new InMemoryConnectionRegistry();
+
+        // Act
+        var removed = registry.RemoveChannel("unknown");
+
+        // Assert
+        Assert.False(removed);
+    }
+
+    [Fact]
+    public void Dispose_DisposesAllChannels()
+    {
+        // Arrange
+        var registry = new InMemoryConnectionRegistry();
+        var channel1 = registry.CreateChannel("conn-1");
+        var channel2 = registry.CreateChannel("conn-2");
+
+        // Act
+        registry.Dispose();
+
+        // Assert
+        Assert.True(channel1.LifetimeToken.IsCancellationRequested);
+        Assert.True(channel2.LifetimeToken.IsCancellationRequested);
+        Assert.Equal(0, registry.Count);
+    }
+}