Add types to settings handling methods (HandlesSettings trait)

[Strift]

The HandlesSettings trait needs improvements regarding return types and parameter definitions.

File: src/Endpoints/Delegates/HandlesSettings.php

Action:

• getSeparatorTokens(): Add PHPDoc @return list<non-empty-string>.
• getEmbedders(): Add PHPDoc defining the embedder array shape.
• updateEmbedders(array $embedders): Add PHPDoc defining the embedder array shape.

File: src/Endpoints/Delegates/HandlesSystem.php

• generateTenantToken: Add type hint array|object for $searchRules.
• swapIndexes: Add PHPDoc @param list<array{string, string}> $indexes.