refactor(tests): remove redundant tests and fix assertion style

Remove subset/duplicate architecture tests already covered by broader
checks, and replace assertTrue(true) with self::addToAssertionCount(1)
for explicit no-exception-thrown intent.

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

lib/Repository/Audit/ImportAuditRunRepository.php

@@ -5,6 +5,7 @@ namespace MintyPHP\Repository\Audit;
 use MintyPHP\DB;
 use MintyPHP\Domain\Taxonomy\ImportAuditStatus;
 use MintyPHP\Repository\Support\RepoQuery;
+use MintyPHP\Repository\Support\RepositoryArrayHelper;
 
 /** Tracks CSV import runs including source file, row counts, status, and completion metadata. */
 class ImportAuditRunRepository implements ImportAuditRunRepositoryInterface
@@ -202,7 +203,7 @@ class ImportAuditRunRepository implements ImportAuditRunRepositoryInterface
         $users = [];
         if (is_array($userRows)) {
             foreach ($userRows as $row) {
-                $flat = self::flattenRow($row);
+                $flat = RepositoryArrayHelper::flattenRow($row);
                 $id = (int) ($flat['user_id'] ?? 0);
                 if ($id <= 0) {
                     continue;
@@ -298,24 +299,4 @@ class ImportAuditRunRepository implements ImportAuditRunRepositoryInterface
         return $item;
     }
 
-    /**
-     * @return array<string, mixed>
-     */
-    private static function flattenRow(mixed $row): array
-    {
-        if (!is_array($row)) {
-            return [];
-        }
-
-        $flat = [];
-        foreach ($row as $key => $value) {
-            if (is_array($value)) {
-                $flat = array_merge($flat, $value);
-            } elseif (is_string($key)) {
-                $flat[$key] = $value;
-            }
-        }
-
-        return $flat;
-    }
 }