Add title field to Resource and ResourceTemplate (#301)

The MCP specification (2025-11-25) defines an optional title field for
Resource and ResourceTemplate as a human-readable display label, distinct
from name (a short identifier). Tool and Prompt already implement this
field; Resource and ResourceTemplate were missing it.

Changes:
- Add title parameter to Resource and ResourceTemplate constructors
- Add title to fromArray(), jsonSerialize(), and PHPStan type arrays
- Add title to McpResource and McpResourceTemplate attributes
- Pass title through Discoverer when constructing schema objects
- Add tests for deserialization, serialization, and null omission

Fixes #296

tests/Unit/Schema/ResourceTest.php

@@ -77,10 +77,45 @@ class ResourceTest extends TestCase
         $this->assertInstanceOf(Resource::class, $resource);
         $this->assertSame(self::VALID_URI, $resource->uri);
         $this->assertSame('list-books', $resource->name);
+        $this->assertNull($resource->title);
         $this->assertNull($resource->description);
         $this->assertNull($resource->meta);
     }
 
+    public function testTitleFromArray(): void
+    {
+        $resource = Resource::fromArray([
+            'uri' => self::VALID_URI,
+            'name' => 'list-books',
+            'title' => 'Book Listing',
+        ]);
+
+        $this->assertSame('Book Listing', $resource->title);
+    }
+
+    public function testTitleSerialization(): void
+    {
+        $resource = new Resource(
+            uri: self::VALID_URI,
+            name: 'list-books',
+            title: 'Book Listing',
+        );
+
+        $data = $resource->jsonSerialize();
+        $this->assertSame('Book Listing', $data['title']);
+    }
+
+    public function testTitleOmittedWhenNull(): void
+    {
+        $resource = new Resource(
+            uri: self::VALID_URI,
+            name: 'list-books',
+        );
+
+        $data = $resource->jsonSerialize();
+        $this->assertArrayNotHasKey('title', $data);
+    }
+
     #[DataProvider('provideInvalidResources')]
     public function testFromArrayInvalid(array $input, string $expectedExceptionMessage): void
     {