Scaffold SevenDaysToDie game stubs

Add empty per-component subdirectories under src/{Analyser,Log,Parser,Pattern}/SevenDaysToDie/
with .gitkeep markers, plus SevenDaysToDieDetective stub extending the base Detective with
a TODO body. Smoke test under test/tests/Games/SevenDaysToDie/ asserts the detective is
instantiable. Directory name is alphabetic because PHP class names cannot begin with a digit.

test/tests/Games/SevenDaysToDie/SmokeTest.php

@@ -0,0 +1,15 @@
+<?php
+
+namespace IndifferentKetchup\Codex\Test\Tests\Games\SevenDaysToDie;
+
+use IndifferentKetchup\Codex\Detective\SevenDaysToDie\SevenDaysToDieDetective;
+use PHPUnit\Framework\TestCase;
+
+class SmokeTest extends TestCase
+{
+    public function testDetectiveIsInstantiable(): void
+    {
+        $detective = new SevenDaysToDieDetective();
+        $this->assertInstanceOf(SevenDaysToDieDetective::class, $detective);
+    }
+}