docs: neutral client wording in the plugin header and the spec (T16)

The header says "mit OAuth für KI-Assistenten" like the readme; the spec names
the client neutrally and keeps claude.ai only where the connector is meant.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

tests/Unit/PluginHeaderTest.php

@@ -0,0 +1,20 @@
+<?php
+
+declare(strict_types=1);
+
+namespace LIT\MCP\Tests\Unit;
+
+use LIT\MCP\Plugin;
+
+/** The plugin header: version in step with Plugin::VERSION, neutral wording (no chatbot branding). */
+final class PluginHeaderTest extends TestCase
+{
+    public function testHeaderIsNeutralAndVersioned(): void
+    {
+        $header = (string) file_get_contents(dirname(__DIR__, 2) . '/wp-lit-mcp.php', false, null, 0, 1024);
+
+        self::assertMatchesRegularExpression('/^ \* Description: .*KI-Assistenten\.$/m', $header);
+        self::assertStringNotContainsString('claude', strtolower($header));
+        self::assertStringContainsString(' * Version: ' . Plugin::VERSION . "\n", $header);
+    }
+}