fix: wrap bare intersection types in parentheses when adding nullable (#1756)

When a MorphTo relation's docblock uses a bare intersection type in the
generic parameter (e.g. `MorphTo<BaseModel&CanBeAssigned, $this>`), the
generated property type incorrectly becomes `BaseModel&CanBeAssigned|null`
instead of the correct `(BaseModel&CanBeAssigned)|null`.

This adds `wrapIntersectionType()` which ensures bare intersection types
are wrapped in parentheses before `|null` is appended, producing valid
DNF type syntax. Applied in both `setProperty()` and `applyNullability()`.

tests/Console/ModelsCommand/MorphToIntersection/Test.php

@@ -0,0 +1,24 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Barryvdh\LaravelIdeHelper\Tests\Console\ModelsCommand\MorphToIntersection;
+
+use Barryvdh\LaravelIdeHelper\Console\ModelsCommand;
+use Barryvdh\LaravelIdeHelper\Tests\Console\ModelsCommand\AbstractModelsCommand;
+
+class Test extends AbstractModelsCommand
+{
+    public function test(): void
+    {
+        $command = $this->app->make(ModelsCommand::class);
+
+        $tester = $this->runCommand($command, [
+            '--write' => true,
+        ]);
+
+        $this->assertSame(0, $tester->getStatusCode());
+        $this->assertStringContainsString('Written new phpDocBlock to', $tester->getDisplay());
+        $this->assertMatchesMockedSnapshot();
+    }
+}