feat(server): Rework transport architecture and add StreamableHttpTransport (#49)

* feat(server): Rework transport architecture and add StreamableHttpTransport

- `Server::connect()` no longer contains a processing loop.
- `TransportInterface` is updated with `setMessageHandler()` and `listen()`.
- `StdioTransport` is updated to implement the new interface.
- A new, minimal `StreamableHttpTransport` is added for stateless HTTP.

* refactor(server): use  event-driven message handling

* feat(server): Introduce a formal session management system

* fix: ensure session elements are preserved when building server (regression from #46)

* refactor: consolidate HTTP example to use shared dependencies

* feat(server): Enhance message handling with session support

- Updated `TransportInterface` to use `onMessage` for handling incoming messages with session IDs.
- Refactored `Server`, `Handler`, and transport classes to accommodate session management using `Uuid`.
- Introduced methods for creating sessions with auto-generated and specific UUIDs in `SessionFactory` and `SessionFactoryInterface`.

* feat(server): Integrate session management in message handling

- Added session support to the `Server` and `Handler` classes, allowing for session data to be managed during message processing.
- Updated `TransportInterface` to include session context in the `send` method.
- Refactored various request handlers to utilize session information, ensuring proper session handling for incoming requests.
- Introduced a file-based session store for persistent session data management

* feat: Update session builder method to use set* instead of with*

* feat: Fix test compatibility with new session management architecture

* chore: apply code style fixes

* fix: remove deprecated SSE transport and resolve PHPStan issues

tests/ServerTest.php

@@ -33,15 +33,20 @@ class ServerTest extends TestCase
             ->onlyMethods(['process'])
             ->getMock();
 
-        $handler->expects($this->exactly(2))->method('process')->willReturnOnConsecutiveCalls(new Exception(new \JsonException('foobar')), ['success']);
+        $handler->expects($this->exactly(2))->method('process')->willReturnOnConsecutiveCalls(
+            new Exception(new \JsonException('foobar')),
+            [['success', []]]
+        );
 
         $transport = $this->getMockBuilder(InMemoryTransport::class)
             ->setConstructorArgs([['foo', 'bar']])
             ->onlyMethods(['send'])
             ->getMock();
-        $transport->expects($this->once())->method('send')->with('success');
+        $transport->expects($this->once())->method('send')->with('success', []);
 
         $server = new Server($handler, $logger);
         $server->connect($transport);
+
+        $transport->listen();
     }
 }