Clean up namespaces (#410)

No meaningful code changes, just lots of namespace shuffling to have fewer namespaces and to put things in better namespaces.

src/ModelContextProtocol/Client/StdioClientTransportOptions.cs

@@ -0,0 +1,64 @@
+namespace ModelContextProtocol.Client;
+
+/// <summary>
+/// Provides options for configuring <see cref="StdioClientTransport"/> instances.
+/// </summary>
+public record StdioClientTransportOptions
+{
+    /// <summary>
+    /// Gets or sets the command to execute to start the server process.
+    /// </summary>
+    public required string Command
+    {
+        get;
+        set
+        {
+            if (string.IsNullOrWhiteSpace(value))
+            {
+                throw new ArgumentException("Command cannot be null or empty.", nameof(value));
+            }
+
+            field = value;
+        }
+    }
+
+    /// <summary>
+    /// Gets or sets the arguments to pass to the server process when it is started.
+    /// </summary>
+    public IList<string>? Arguments { get; set; }
+
+    /// <summary>
+    /// Gets or sets a transport identifier used for logging purposes.
+    /// </summary>
+    public string? Name { get; set; }
+
+    /// <summary>
+    /// Gets or sets the working directory for the server process.
+    /// </summary>
+    public string? WorkingDirectory { get; set; }
+
+    /// <summary>
+    /// Gets or sets environment variables to set for the server process.
+    /// </summary>
+    /// <remarks>
+    /// This property allows you to specify environment variables that will be set in the server process's
+    /// environment. This is useful for passing configuration, authentication information, or runtime flags
+    /// to the server without modifying its code.
+    /// </remarks>
+    public Dictionary<string, string>? EnvironmentVariables { get; set; }
+
+    /// <summary>
+    /// Gets or sets the timeout to wait for the server to shut down gracefully.
+    /// </summary>
+    /// <remarks>
+    /// <para>
+    /// This property dictates how long the client should wait for the server process to exit cleanly during shutdown
+    /// before forcibly terminating it. This balances between giving the server enough time to clean up 
+    /// resources and not hanging indefinitely if a server process becomes unresponsive.
+    /// </para>
+    /// <para>
+    /// The default is five seconds.
+    /// </para>
+    /// </remarks>
+    public TimeSpan ShutdownTimeout { get; set; } = TimeSpan.FromSeconds(5);
+}