Improve progress reporting (#145)

* Improve progress reporting

- Enable injecting an `IProgress<>` into a tool call to report progress when the client has supplied a progress token
- Add a custom type for ProgressToken and ProgressNotification to map to the schema
- Simplify RequestId to match ProgressToken's shape
- Serialize StdioClientTransport's SendMessageAsync implementation
- Add strongly-typed names for all request methods
- Change all request IDs created by McpJsonRpcEndpoint to include a guid for that endpoint

* Address PR feedback

src/ModelContextProtocol/Protocol/Transport/SseClientSessionTransport.cs

@@ -118,7 +118,7 @@ internal sealed class SseClientSessionTransport : TransportBase
         var responseContent = await response.Content.ReadAsStringAsync(cancellationToken).ConfigureAwait(false);
 
         // Check if the message was an initialize request
-        if (message is JsonRpcRequest request && request.Method == "initialize")
+        if (message is JsonRpcRequest request && request.Method == RequestMethods.Initialize)
         {
             // If the response is not a JSON-RPC response, it is an SSE message
             if (responseContent.Equals("accepted", StringComparison.OrdinalIgnoreCase))

src/ModelContextProtocol/Protocol/Transport/StdioClientStreamTransport.cs

@@ -21,6 +21,7 @@ internal sealed class StdioClientStreamTransport : TransportBase
     private readonly ILogger _logger;
     private readonly JsonSerializerOptions _jsonOptions;
     private readonly DataReceivedEventHandler _logProcessErrors;
+    private readonly SemaphoreSlim _sendLock = new(1, 1);
     private Process? _process;
     private Task? _readTask;
     private CancellationTokenSource? _shutdownCts;
@@ -150,6 +151,8 @@ internal sealed class StdioClientStreamTransport : TransportBase
     /// <inheritdoc/>
     public override async Task SendMessageAsync(IJsonRpcMessage message, CancellationToken cancellationToken = default)
     {
+        using var _ = await _sendLock.LockAsync(cancellationToken).ConfigureAwait(false);
+
         if (!IsConnected || _process?.HasExited == true)
         {
             _logger.TransportNotConnected(EndpointName);