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.

src/__Libraries/StellaOps.Router.Common/Models/Frame.cs

@@ -0,0 +1,24 @@
+using StellaOps.Router.Common.Enums;
+
+namespace StellaOps.Router.Common.Models;
+
+/// <summary>
+/// Represents a protocol frame in the router transport layer.
+/// </summary>
+public sealed record Frame
+{
+    /// <summary>
+    /// Gets the type of this frame.
+    /// </summary>
+    public required FrameType Type { get; init; }
+
+    /// <summary>
+    /// Gets the correlation ID for request/response matching.
+    /// </summary>
+    public string? CorrelationId { get; init; }
+
+    /// <summary>
+    /// Gets the raw payload bytes.
+    /// </summary>
+    public ReadOnlyMemory<byte> Payload { get; init; }
+}