(fix): add PHPStan type assertions for Document constructor calls

The $value from getAttribute() is typed as mixed. After array_is_list()
check confirms string keys, PHPStan still needs an explicit assertion.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: abnegate

src/Database/Hook/Relationships.php

@@ -148,6 +148,7 @@ public function afterDocumentCreate(Document $collection, Document $document): D
 
             try {
                 if (\is_array($value) && ! \array_is_list($value)) {
+                    /** @var array<string, mixed> $value */
                     $value = new Document($value);
                     $document->setAttribute($key, $value);
                 }
@@ -286,6 +287,7 @@ public function afterDocumentUpdate(Document $collection, Document $old, Documen
             $value = $document->getAttribute($key);
 
             if (\is_array($value) && ! \array_is_list($value)) {
+                /** @var array<string, mixed> $value */
                 $value = new Document($value);
                 $document->setAttribute($key, $value);
             }