Test MappingName reserved-name and empty-name validation

MappingName gained a reserved "native" check (mirroring SchemaName) that
had only indirect coverage. Add a direct unit test for the empty guard
and the reserved name across casings — the invariant the projection
listing now relies on to stay crash-free.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: JeroenDeDauw

tests/phpunit/Domain/Mapping/MappingNameTest.php

@@ -0,0 +1,47 @@
+<?php
+
+declare( strict_types = 1 );
+
+namespace ProfessionalWiki\NeoWiki\Tests\Domain\Mapping;
+
+use InvalidArgumentException;
+use PHPUnit\Framework\TestCase;
+use ProfessionalWiki\NeoWiki\Domain\Mapping\MappingName;
+
+/**
+ * @covers \ProfessionalWiki\NeoWiki\Domain\Mapping\MappingName
+ */
+class MappingNameTest extends TestCase {
+
+	public function testNonReservedMappingNameIsValid(): void {
+		$mappingName = new MappingName( 'EDM' );
+
+		$this->assertSame( 'EDM', $mappingName->getText() );
+	}
+
+	public function testEmptyMappingNameIsInvalid(): void {
+		$this->expectException( InvalidArgumentException::class );
+
+		new MappingName( '  ' );
+	}
+
+	/**
+	 * "native" is the built-in projection, so a Mapping page may not claim it, in any casing (MediaWiki
+	 * uppercases only the first title letter, so "Native" is the reachable form).
+	 *
+	 * @dataProvider reservedMappingNameProvider
+	 */
+	public function testReservedMappingNameIsInvalid( string $name ): void {
+		$this->expectException( InvalidArgumentException::class );
+
+		new MappingName( $name );
+	}
+
+	public static function reservedMappingNameProvider(): iterable {
+		yield [ 'native' ];
+		yield [ 'Native' ];
+		yield [ 'NATIVE' ];
+		yield [ 'nAtIvE' ];
+	}
+
+}