(fix): CI — emit INSERT IGNORE when skipDuplicates is set in SQL::createDocuments

The MariaDB/MySQL/Postgres/SQLite adapters' shared createDocuments() always
called $builder->insert(), ignoring the skipDuplicates flag. When
Mirror::createDocuments forwarded a batch to destination under
skipDuplicates (to backfill rows where source had INSERT IGNORE them as
no-ops but destination still lacked them), destination crashed with
PDOException 1062 Duplicate entry.

Route through the query builder's insertOrIgnore() when skipDuplicates is
true — it compiles to INSERT IGNORE (MySQL/MariaDB), INSERT OR IGNORE
(SQLite), and INSERT ... ON CONFLICT DO NOTHING (Postgres).

Fixes MirrorTest::testCreateDocumentsSkipDuplicatesBackfillsDestination.

Author: github-actions[bot]

src/Database/Adapter/SQL.php

@@ -628,7 +628,7 @@ public function createDocuments(Document $collection, array $documents): array
                 $builder->set($row);
             }
 
-            $result = $builder->insert();
+            $result = $this->skipDuplicates ? $builder->insertOrIgnore() : $builder->insert();
             $stmt = $this->executeResult($result, Event::DocumentCreate);
             $this->execute($stmt);