* Remove McpServerConfig and have McpClientFactory accept IClientTransport instances directly.
* Address feedback and use lists when representing stdio arguments.
* Use "Name" for transport descriptors and "EndpointName" for MCP clients and servers.
* Update code samples.
* Fix source file naming
* Move notification handler registrations to capabilities
Currently request handlers are set on the capability objects, but notification handlers are set after construction via an AddNotificationHandler method on the IMcpEndpoint interface. This moves handler specification to be at construction as well. This makes it more consistent with request handlers, simplifies the IMcpEndpoint interface to just be about message sending, and avoids a concurrency bug that could occur if someone tried to add a handler while the endpoint was processing notifications.
* Address more feedback and further cleanup
* Add XunitLoggerProvider
* Avoid logging to stale ITestOutputHelper in fixture disposal
* Use LoggedTest base class everywhere an ILoggerFactory is used
