fix: remove int cast from getTenant to fix strict type comparison

Document::getTenant() was casting numeric tenant strings to int,
but Adapter::getTenant() stored the raw string from setTenant().
The strict !== comparison in getCollection() then failed because
(int)1 !== "1", causing "Collection not found" for shared table
projects on SQL adapters.

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

Author: abnegate

src/Database/Document.php

@@ -177,13 +177,7 @@ public function getUpdatedAt(): ?string
      */
     public function getTenant(): int|string|null
     {
-        $tenant = $this->getAttribute('$tenant');
-
-        if (\is_numeric($tenant)) {
-            return (int) $tenant;
-        }
-
-        return $tenant;
+        return $this->getAttribute('$tenant');
     }
 
     /**