[Server] Simplify server entrypoint with run-based transport lifecycle (#103)

* feat: replace connect/listen flow with run lifecycle

* feat(transport): add phpstan generics for typed transport returns

* refactor: standardize variable naming for MCP server instances in transport handling

* test: remove unnecessary phpstan-ignore annotation in DocBlockTestFixture

src/Server/Transport/InMemoryTransport.php

@@ -14,6 +14,8 @@ namespace Mcp\Server\Transport;
 use Symfony\Component\Uid\Uuid;
 
 /**
+ * @implements TransportInterface<null>
+ *
  * @author Tobias Nyholm <tobias.nyholm@gmail.com>
  */
 class InMemoryTransport implements TransportInterface
@@ -50,6 +52,9 @@ class InMemoryTransport implements TransportInterface
         }
     }
 
+    /**
+     * @return null
+     */
     public function listen(): mixed
     {
         foreach ($this->messages as $message) {
@@ -60,6 +65,7 @@ class InMemoryTransport implements TransportInterface
 
         if (\is_callable($this->sessionDestroyListener) && null !== $this->sessionId) {
             \call_user_func($this->sessionDestroyListener, $this->sessionId);
+            $this->sessionId = null;
         }
 
         return null;
@@ -74,6 +80,7 @@ class InMemoryTransport implements TransportInterface
     {
         if (\is_callable($this->sessionDestroyListener) && null !== $this->sessionId) {
             \call_user_func($this->sessionDestroyListener, $this->sessionId);
+            $this->sessionId = null;
         }
     }
 }

src/Server/Transport/StdioTransport.php

@@ -16,6 +16,8 @@ use Psr\Log\NullLogger;
 use Symfony\Component\Uid\Uuid;
 
 /**
+ * @implements TransportInterface<int>
+ *
  * @author Kyrian Obikwelu <koshnawaza@gmail.com>
  */
 class StdioTransport implements TransportInterface
@@ -59,13 +61,18 @@ class StdioTransport implements TransportInterface
         fwrite($this->output, $data.\PHP_EOL);
     }
 
-    public function listen(): mixed
+    public function listen(): int
     {
         $this->logger->info('StdioTransport is listening for messages on STDIN...');
 
+        $status = 0;
         while (!feof($this->input)) {
             $line = fgets($this->input);
             if (false === $line) {
+                if (!feof($this->input)) {
+                    $status = 1;
+                }
+
                 break;
             }
 
@@ -82,9 +89,10 @@ class StdioTransport implements TransportInterface
 
         if (\is_callable($this->sessionEndListener) && null !== $this->sessionId) {
             \call_user_func($this->sessionEndListener, $this->sessionId);
+            $this->sessionId = null;
         }
 
-        return null;
+        return $status;
     }
 
     public function onSessionEnd(callable $listener): void
@@ -96,6 +104,7 @@ class StdioTransport implements TransportInterface
     {
         if (\is_callable($this->sessionEndListener) && null !== $this->sessionId) {
             \call_user_func($this->sessionEndListener, $this->sessionId);
+            $this->sessionId = null;
         }
 
         if (\is_resource($this->input)) {

src/Server/Transport/StreamableHttpTransport.php

@@ -21,6 +21,8 @@ use Psr\Log\NullLogger;
 use Symfony\Component\Uid\Uuid;
 
 /**
+ * @implements TransportInterface<ResponseInterface>
+ *
  * @author Kyrian Obikwelu <koshnawaza@gmail.com>
  */
 class StreamableHttpTransport implements TransportInterface
@@ -78,7 +80,7 @@ class StreamableHttpTransport implements TransportInterface
         ]);
     }
 
-    public function listen(): mixed
+    public function listen(): ResponseInterface
     {
         return match ($this->request->getMethod()) {
             'OPTIONS' => $this->handleOptionsRequest(),

src/Server/Transport/TransportInterface.php

@@ -14,6 +14,8 @@ namespace Mcp\Server\Transport;
 use Symfony\Component\Uid\Uuid;
 
 /**
+ * @template TResult
+ *
  * @author Christopher Hertel <mail@christopher-hertel.de>
  * @author Kyrian Obikwelu <koshnawaza@gmail.com>
  */
@@ -38,7 +40,7 @@ interface TransportInterface
      * - For a single-request transport like HTTP, this will process the request
      *   and return a result (e.g., a PSR-7 Response) to be sent to the client.
      *
-     * @return mixed the result of the transport's execution, if any
+     * @return TResult the result of the transport's execution, if any
      */
     public function listen(): mixed;
 
@@ -63,6 +65,7 @@ interface TransportInterface
      *
      * This method should be called when the transport is no longer needed.
      * It should clean up any resources and close any connections.
+     * `Server::run()` calls this automatically after `listen()` exits.
      */
     public function close(): void;
 }