Missing support for attachments to AutomationDocuments

This would support modular code in projects with multiple `ExecuteScriptStep` step files already in use.
From what I understand the attachment file needs to be added to the document and the step itself.

Start by tracing AutomationDocuments and ExecuteScriptStep in the TypeScript project to understand how document content and steps are represented. Determine how an attachment file must be associated with both, then verify that a document using multiple ExecuteScriptStep files includes the attachment correctly.

Written by the indexing model from the issue text.