examples: add a 'listeverything' client example, and reorganize

Add a client example that lists all features on a stdio server. Since
this is our first client example, organize examples by client / server
-- otherwise it is too difficult to find client examples.

For #33

examples/server/hello/main.go

@@ -0,0 +1,90 @@
+// Copyright 2025 The Go MCP SDK Authors. All rights reserved.
+// Use of this source code is governed by an MIT-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import (
+	"context"
+	"flag"
+	"fmt"
+	"log"
+	"net/http"
+	"net/url"
+	"os"
+
+	"github.com/modelcontextprotocol/go-sdk/mcp"
+)
+
+var httpAddr = flag.String("http", "", "if set, use streamable HTTP at this address, instead of stdin/stdout")
+
+type HiArgs struct {
+	Name string `json:"name" jsonschema:"the name to say hi to"`
+}
+
+func SayHi(ctx context.Context, ss *mcp.ServerSession, params *mcp.CallToolParamsFor[HiArgs]) (*mcp.CallToolResultFor[struct{}], error) {
+	return &mcp.CallToolResultFor[struct{}]{
+		Content: []mcp.Content{
+			&mcp.TextContent{Text: "Hi " + params.Arguments.Name},
+		},
+	}, nil
+}
+
+func PromptHi(ctx context.Context, ss *mcp.ServerSession, params *mcp.GetPromptParams) (*mcp.GetPromptResult, error) {
+	return &mcp.GetPromptResult{
+		Description: "Code review prompt",
+		Messages: []*mcp.PromptMessage{
+			{Role: "user", Content: &mcp.TextContent{Text: "Say hi to " + params.Arguments["name"]}},
+		},
+	}, nil
+}
+
+func main() {
+	flag.Parse()
+
+	server := mcp.NewServer(&mcp.Implementation{Name: "greeter"}, nil)
+	mcp.AddTool(server, &mcp.Tool{Name: "greet", Description: "say hi"}, SayHi)
+	server.AddPrompt(&mcp.Prompt{Name: "greet"}, PromptHi)
+	server.AddResource(&mcp.Resource{
+		Name:     "info",
+		MIMEType: "text/plain",
+		URI:      "embedded:info",
+	}, handleEmbeddedResource)
+
+	if *httpAddr != "" {
+		handler := mcp.NewStreamableHTTPHandler(func(*http.Request) *mcp.Server {
+			return server
+		}, nil)
+		log.Printf("MCP handler listening at %s", *httpAddr)
+		http.ListenAndServe(*httpAddr, handler)
+	} else {
+		t := mcp.NewLoggingTransport(mcp.NewStdioTransport(), os.Stderr)
+		if err := server.Run(context.Background(), t); err != nil {
+			log.Printf("Server failed: %v", err)
+		}
+	}
+}
+
+var embeddedResources = map[string]string{
+	"info": "This is the hello example server.",
+}
+
+func handleEmbeddedResource(_ context.Context, _ *mcp.ServerSession, params *mcp.ReadResourceParams) (*mcp.ReadResourceResult, error) {
+	u, err := url.Parse(params.URI)
+	if err != nil {
+		return nil, err
+	}
+	if u.Scheme != "embedded" {
+		return nil, fmt.Errorf("wrong scheme: %q", u.Scheme)
+	}
+	key := u.Opaque
+	text, ok := embeddedResources[key]
+	if !ok {
+		return nil, fmt.Errorf("no embedded resource named %q", key)
+	}
+	return &mcp.ReadResourceResult{
+		Contents: []*mcp.ResourceContents{
+			{URI: params.URI, MIMEType: "text/plain", Text: text},
+		},
+	}, nil
+}