[Examples][Tests] Make the MCP Apps example work over HTTP, and pin it (#439)

* [Examples][Tests] Make the MCP Apps example work over HTTP, and pin it

It was the only example without a session store, so every request under
`php -S` or php-fpm - each its own process - was answered "Session not found
or has expired". It now uses a FileSessionStore like the others.

Inspector snapshots pin what the extension actually puts on the wire: the
ui:// resource's `text/html;profile=mcp-app` MIME type and `ui` marker, and
the `_meta.ui` on the tool that links the two.

* Apply suggestion from @chr-hertel

* Apply suggestion from @chr-hertel

tests/Inspector/Http/HttpMcpAppsTest.php

@@ -0,0 +1,50 @@
+<?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.
+ */
+
+namespace Mcp\Tests\Inspector\Http;
+
+/**
+ * Snapshots the MCP Apps example as the Inspector sees it.
+ *
+ * What the snapshots are actually pinning is the extension's metadata surviving
+ * registration: the `ui://` resource carrying `text/html;profile=mcp-app` and
+ * the `ui` marker in its `_meta`, and the tool carrying the `UiToolMeta` that
+ * links it to that resource. Those are the two halves a host needs to render an
+ * app, and both travel in `_meta`, where a silent drop would otherwise go
+ * unnoticed until a host failed to render anything.
+ */
+final class HttpMcpAppsTest extends HttpInspectorSnapshotTestCase
+{
+    public static function provideMethods(): array
+    {
+        return [
+            ...parent::provideMethods(),
+            'Read the UI resource' => [
+                'method' => 'resources/read',
+                'options' => ['uri' => 'ui://weather-app'],
+                'testName' => 'weather_app',
+            ],
+            'Call the linked tool' => [
+                'method' => 'tools/call',
+                'options' => [
+                    'toolName' => 'get_weather',
+                    'toolArgs' => ['city' => 'london'],
+                ],
+                'testName' => 'get_weather',
+            ],
+        ];
+    }
+
+    protected function getServerScript(): string
+    {
+        return \dirname(__DIR__, 3).'/examples/server/mcp-apps/server.php';
+    }
+}