chore(dev): remove broken auto-run PHPUnit hook

The PostToolUse hook called php bin/phpunit directly, which does not
work inside the Docker-based dev setup. Remove it; tests should be
run via docker compose exec graph vendor/bin/phpunit as documented.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.claude/settings.json

@@ -1,10 +1 @@
-{
-    "hooks": {
-        "PostToolUse": [
-            {
-                "matcher": "Edit|Write",
-                "command": "php bin/phpunit 2>&1 | tail -20"
-            }
-        ]
-    }
-}
+{}