[Client] Feat: Implement MCP client component (#192)

* feat(client): add complete MCP client SDK with STDIO and HTTP transports

Add Client, Builder, ClientProtocol, ClientSession, and transport
implementations for communicating with MCP servers. Supports tools, resources, prompts, and real-time progress/logging notifications.

* refactor(examples): reorganize examples into server/ and client/ folders

* feat: add SamplingRequestHandler for handling server sampling requests

* feat: add setLoggingLevel method to control server logging verbosity

* refactor: make progress token dependent on request ID

* docs: Update server IP in usage instructions and add notes on sampling server requirements.

* feat: add complete() method for completion/complete requests

* refactor: properly parse and type initialize result

* refactor: standardize method names

* fix: revert changes to server related components

* fix: revert changes to server related components

* refactor: Restructure client transports and handlers into dedicated namespaces.

* fix: cs and php-stan errors fixes(partial)

* feat: Refactor request handlers to return `Response` or `Error` objects directly, adding a `SamplingException` and error logging for sampling requests.

* feat: Replace `ClientTransportInterface` with `TransportInterface` and move response result deserialization to client methods.

* refactor: remove redundant timeout check for intialize on transports

The processFiber that executes per tick while fiber is suspended already handles timeouts while waiting

* feat: broaden symfony/http-client dependency to support Symfony 5.4 to 8.0

* Update examples/client/README.md

Co-authored-by: Christopher Hertel <mail@christopher-hertel.de>

* Update examples/client/README.md

Co-authored-by: Christopher Hertel <mail@christopher-hertel.de>

* refactor: remove outgoing message queue from session and simplify transport send method to directly dispatch messages.

* refactor: Replace ClientSession with ClientState for clearer intent on runtime state management

* refactor: rename connectAndInitialize to connect for consistency

* chore: cs fix

* chore: use SamplingCallbackInterface instead of a closure for sampling request handler

---------

Co-authored-by: Christopher Hertel <mail@christopher-hertel.de>

examples/client/http_discovery_calculator.php

@@ -0,0 +1,77 @@
+<?php
+
+/**
+ * HTTP Client Example.
+ *
+ * This example demonstrates how to use the MCP client with an HTTP transport
+ * to communicate with a remote MCP server over HTTP.
+ *
+ * Usage: php examples/client/http_discovery_calculator.php
+ *
+ * Before running, start an HTTP MCP server:
+ *   php -S localhost:8080 examples/server/http-discovery-calculator/server.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 __DIR__.'/../../vendor/autoload.php';
+
+use Mcp\Client;
+use Mcp\Client\Transport\HttpTransport;
+
+$endpoint = 'http://localhost:8000';
+
+$client = Client::builder()
+    ->setClientInfo('HTTP Example Client', '1.0.0')
+    ->setInitTimeout(30)
+    ->setRequestTimeout(60)
+    ->build();
+
+$transport = new HttpTransport($endpoint);
+
+try {
+    echo "Connecting to MCP server at {$endpoint}...\n";
+    $client->connect($transport);
+
+    echo "Connected! Server info:\n";
+    $serverInfo = $client->getServerInfo();
+    echo '  Name: '.($serverInfo->name ?? 'unknown')."\n";
+    echo '  Version: '.($serverInfo->version ?? 'unknown')."\n\n";
+
+    echo "Available tools:\n";
+    $toolsResult = $client->listTools();
+    foreach ($toolsResult->tools as $tool) {
+        echo "  - {$tool->name}: {$tool->description}\n";
+    }
+    echo "\n";
+
+    echo "Available resources:\n";
+    $resourcesResult = $client->listResources();
+    foreach ($resourcesResult->resources as $resource) {
+        echo "  - {$resource->uri}: {$resource->name}\n";
+    }
+    echo "\n";
+
+    echo "Available prompts:\n";
+    $promptsResult = $client->listPrompts();
+    foreach ($promptsResult->prompts as $prompt) {
+        echo "  - {$prompt->name}: {$prompt->description}\n";
+    }
+    echo "\n";
+} catch (Throwable $e) {
+    echo "Error: {$e->getMessage()}\n";
+    echo $e->getTraceAsString()."\n";
+} finally {
+    echo "Disconnecting...\n";
+    $client->disconnect();
+    echo "Done.\n";
+}