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/env-variables/server.php

@@ -1,61 +0,0 @@
-#!/usr/bin/env php
-<?php
-
-/*
- * 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;
-
-/*
-    |--------------------------------------------------------------------------
-    | MCP Environment Variable Example Server
-    |--------------------------------------------------------------------------
-    |
-    | This server demonstrates how to use environment variables to modify tool
-    | behavior. The MCP client can set the APP_MODE environment variable to
-    | control the server's behavior.
-    |
-    | Configure your MCP Client (e.g. Cursor) for this server like this:
-    |
-    | {
-    |     "mcpServers": {
-    |         "my-php-env-server": {
-    |             "command": "php",
-    |             "args": ["/full/path/to/examples/05-stdio-env-variables/server.php"],
-    |             "env": {
-    |                 "APP_MODE": "debug" // or "production", or leave it out
-    |             }
-    |         }
-    |     }
-    | }
-    |
-    | The server will read the APP_MODE environment variable and use it to
-    | modify the behavior of the tools.
-    |
-    | If the APP_MODE environment variable is not set, the server will use the
-    | default behavior.
-    |
-*/
-
-logger()->info('Starting MCP Environment Variable Example Server...');
-
-$server = Server::builder()
-    ->setServerInfo('Env Var Server', '1.0.0')
-    ->setLogger(logger())
-    ->setDiscovery(__DIR__)
-    ->build();
-
-$result = $server->run(transport());
-
-logger()->info('Server listener stopped gracefully.', ['result' => $result]);
-
-shutdown($result);