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.

docs/router/README.md

@@ -0,0 +1,62 @@
+# StellaOps Router
+
+The StellaOps Router is the internal communication infrastructure that enables microservices to communicate through a central gateway.
+
+## Overview
+
+The router provides:
+
+- **Gateway WebService** (`StellaOps.Gateway.WebService`): HTTP ingress service that routes requests to microservices
+- **Microservice SDK** (`StellaOps.Microservice`): SDK for building microservices that connect to the router
+- **Transport Plugins**: Multiple transport options (TCP, TLS, UDP, RabbitMQ, InMemory for testing)
+- **Claims-based Authorization**: Using `RequiringClaims` instead of role-based access
+
+## Key Documents
+
+| Document | Purpose |
+|----------|---------|
+| [specs.md](./specs.md) | **Canonical specification** - READ FIRST |
+| [implplan.md](./implplan.md) | High-level implementation plan |
+| [SPRINT_INDEX.md](./SPRINT_INDEX.md) | Sprint overview and dependency graph |
+
+## Solution Structure
+
+```
+StellaOps.Router.slnx
+├── src/__Libraries/
+│   ├── StellaOps.Router.Common/     # Shared types, enums, interfaces
+│   ├── StellaOps.Router.Config/     # Router configuration models
+│   ├── StellaOps.Microservice/      # Microservice SDK
+│   └── StellaOps.Microservice.SourceGen/  # Build-time endpoint discovery
+├── src/Gateway/
+│   └── StellaOps.Gateway.WebService/  # HTTP gateway service
+└── tests/
+    ├── StellaOps.Router.Common.Tests/
+    ├── StellaOps.Gateway.WebService.Tests/
+    └── StellaOps.Microservice.Tests/
+```
+
+## Building
+
+```bash
+# Build the router solution
+dotnet build StellaOps.Router.slnx
+
+# Run tests
+dotnet test StellaOps.Router.slnx
+```
+
+## Invariants (Non-Negotiable)
+
+From the specification, these are non-negotiable:
+
+- **Method + Path** is the endpoint identity
+- **Strict semver** for version matching
+- **Region from GatewayNodeConfig.Region** (never from headers/host)
+- **No HTTP transport** between gateway and microservices
+- **RequiringClaims** (not AllowedRoles) for authorization
+- **Opaque body handling** (router doesn't interpret payloads)
+
+## Status
+
+Currently in development. See [SPRINT_INDEX.md](./SPRINT_INDEX.md) for implementation progress.