Add PSR-4 autoload-dev configuration for tests

Add autoload-dev section to composer.json to properly map test
namespace ShipMonkTests\PHPStanDev\ to tests/ directory following
PSR-4 conventions.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>

Author: JanTvrdik

composer.json

@@ -33,6 +33,11 @@
             "ShipMonk\\PHPStanDev\\": "src/"
         }
     },
+    "autoload-dev": {
+        "psr-4": {
+            "ShipMonkTests\\PHPStanDev\\": "tests/"
+        }
+    },
     "config": {
         "allow-plugins": {
             "dealerdirect/phpcodesniffer-composer-installer": false,