Add types to document handling methods (HandlesDocuments trait)

[Strift]

The HandlesDocuments trait contains several methods with generic array parameters or missing return types.

File: src/Endpoints/Delegates/HandlesDocuments.php

Action:

• getDocument(...): Add PHPDoc @return array<string, mixed>.
• addDocuments(array $documents, ...): Add PHPDoc @param list<array<string, mixed>> $documents.
• updateDocuments(array $documents, ...): Add PHPDoc @param list<array<string, mixed>> $documents.
• deleteDocuments(array $options): Add PHPDoc for expected $options shape.
• addDocumentsInBatches: Add specific array type PHPDoc.
• updateDocumentsInBatches: Add specific array type PHPDoc.