Move examples to server directory (#198)

* move examples to server directory

This will prepare for the client implementation in https://github.com/modelcontextprotocol/php-sdk/pull/192

* fix move bootstrap too

examples/server/cached-discovery/CachedCalculatorElements.php

@@ -0,0 +1,54 @@
+<?php
+
+declare(strict_types=1);
+
+/*
+ * This file is part of the official PHP MCP SDK.
+ *
+ * A collaboration between Symfony and the PHP Foundation.
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Mcp\Example\Server\CachedDiscovery;
+
+use Mcp\Capability\Attribute\McpTool;
+use Mcp\Exception\ToolCallException;
+
+/**
+ * Example MCP elements for demonstrating cached discovery.
+ *
+ * This class contains simple calculator tools that will be discovered
+ * and cached for improved performance on subsequent server starts.
+ */
+class CachedCalculatorElements
+{
+    #[McpTool(name: 'add_numbers')]
+    public function add(int $a, int $b): int
+    {
+        return $a + $b;
+    }
+
+    #[McpTool(name: 'multiply_numbers')]
+    public function multiply(int $a, int $b): int
+    {
+        return $a * $b;
+    }
+
+    #[McpTool(name: 'divide_numbers')]
+    public function divide(int $a, int $b): float
+    {
+        if (0 === $b) {
+            throw new ToolCallException('Division by zero is not allowed');
+        }
+
+        return $a / $b;
+    }
+
+    #[McpTool(name: 'power')]
+    public function power(int $base, int $exponent): int
+    {
+        return (int) $base ** $exponent;
+    }
+}

examples/server/cached-discovery/server.php

@@ -0,0 +1,37 @@
+#!/usr/bin/env php
+<?php
+
+declare(strict_types=1);
+
+/*
+ * This file is part of the official PHP MCP SDK.
+ *
+ * A collaboration between Symfony and the PHP Foundation.
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+require_once dirname(__DIR__).'/bootstrap.php';
+chdir(__DIR__);
+
+use Mcp\Server;
+use Mcp\Server\Session\FileSessionStore;
+use Symfony\Component\Cache\Adapter\PhpFilesAdapter;
+use Symfony\Component\Cache\Psr16Cache;
+
+logger()->info('Starting MCP Cached Discovery Calculator Server...');
+
+$server = Server::builder()
+    ->setServerInfo('Cached Discovery Calculator', '1.0.0', 'Calculator with cached discovery for better performance.')
+    ->setContainer(container())
+    ->setSession(new FileSessionStore(__DIR__.'/sessions'))
+    ->setLogger(logger())
+    ->setDiscovery(__DIR__, cache: new Psr16Cache(new PhpFilesAdapter(directory: __DIR__.'/cache')))
+    ->build();
+
+$result = $server->run(transport());
+
+logger()->info('Server listener stopped gracefully.', ['result' => $result]);
+
+shutdown($result);