Overhaul tool handling (#89)

* Overhaul tool handling

- Renames [McpTool{Type}] to [McpServerTool{Type}], in order to distinguish representations of tools on the server from tools on the client.
- Enables [McpServerTool] methods to have arguments injected from DI, as well as a specific set of types from the implementation directly, like IMcpServer.
- Renames WithTools to WithToolsFromAssembly.
- All of the WithToolsXx methods now publish each individual McpServerTool into DI; other code can do so as well. The options setup code gathers all of the tools from DI and combines them into a collection which is then stored in McpServerOptions and used to construct the server.
- The server tools specified via DI as well as manually-provided handlers, using CallToolHandler as a fallback in case the requested tool doesn't exist in the tools collection, and ListToolsHandler augments the information for whatever tools exist.
- The tools are stored in McpServerOptions in a new McpServerToolCollection type, which is a thread-safe container that exposes add/removal notification. Adding/removing tools triggers a change notification that in turn sends a notification to the client about a tools update.
- The ServerOptions are exposed from the server instance.
- Removed cursor-based APIs from McpClientExtensions.
- Changed McpClientExtensions APIs to return `Task<IList<...>` rather than `IAsyncEnumerable<...>`.

I'm sure this will need to evolve further before we're "done", but it's a significant improvement from where we are now. One area I'm not super happy with is the notifying collection; that might work ok for a stdio server, where you can grab the created collection from the server's options and mutate it, but I don't know how well that's going to work for sse servers.

* Make McpServerTool{Collection} extensible

* Fix README.md example

* Add notifications test

* Address feedback

samples/TestServerWithHosting/Program.cs

@@ -19,7 +19,7 @@ try
     builder.Services.AddSerilog();
     builder.Services.AddMcpServer()
         .WithStdioServerTransport()
-        .WithTools();
+        .WithToolsFromAssembly();
 
     var app = builder.Build();
 

samples/TestServerWithHosting/Tools/EchoTool.cs

@@ -3,10 +3,10 @@ using System.ComponentModel;
 
 namespace TestServerWithHosting.Tools;
 
-[McpToolType]
+[McpServerToolType]
 public static class EchoTool
 {
-    [McpTool, Description("Echoes the input back to the client.")]
+    [McpServerTool, Description("Echoes the input back to the client.")]
     public static string Echo(string message)
     {
         return "hello " + message;

samples/TestServerWithHosting/Tools/SampleLlmTool.cs

@@ -7,7 +7,7 @@ namespace TestServerWithHosting.Tools;
 /// <summary>
 /// This tool uses depenency injection and async method
 /// </summary>
-[McpToolType]
+[McpServerToolType]
 public class SampleLlmTool
 {
     private readonly IMcpServer _server;
@@ -17,7 +17,7 @@ public class SampleLlmTool
         _server = server ?? throw new ArgumentNullException(nameof(server));
     }
 
-    [McpTool("sampleLLM"), Description("Samples from an LLM using MCP's sampling feature")]
+    [McpServerTool("sampleLLM"), Description("Samples from an LLM using MCP's sampling feature")]
     public async Task<string> SampleLLM(
         [Description("The prompt to send to the LLM")] string prompt,
         [Description("Maximum number of tokens to generate")] int maxTokens,