[Hold] SMB transform UI experience

[Paul-Cornell]

Coordinate merge of this PR with public availability of the associated features.

Main articles for review:

• "Transform experience" UI quickstart: https://unstructured-53-doc-38-smb-ux.mintlify.app/welcome#unstructured-ui-quickstart
• Transform experience UI walkthrough (post-quickstart): https://unstructured-53-doc-38-smb-ux.mintlify.app/ui/walkthrough-2
• "Generative OCR" enrichment explainer: https://unstructured-53-doc-38-smb-ux.mintlify.app/ui/enriching/generative-ocr
• How to add a generative OCR enrichment to a custom workflow: https://unstructured-53-doc-38-smb-ux.mintlify.app/ui/workflows#enrichment-node

(Adding here for completeness...) Other articles with minor impacts (no need to review):

• Suggest the Workflow Endpoint quickstart as an alternative to the Partition Endpoint quickstart. See the end of the first green Tip in https://unstructured-53-doc-38-smb-ux.mintlify.app/api-reference/partition/quickstart
• Link to the open-source limits section from the API Reference overview, answering the question "why not use the open-source library instead of this API?" See the "Learn more" link in https://unstructured-53-doc-38-smb-ux.mintlify.app/api-reference/overview#benefits-over-open-source