AI writing assistant for Documents and Dashboards

**What problem will this feature request solve?**
The Documents editor has no AI help for the narrative text. Users have to leave Metabase to draft or polish the prose around their charts and queries.

**Describe the solution you'd like.**
An AI writing assistant available directly inside a Document that can draft, rewrite, improve tone, and fix grammar of the document narrative — similar to the AI writers people use in some other editors

**How does this feature request impact you?**
It's an ease-of-use ask. The customer reports their own clients have asked about this during demos and trainings.

**Additional information**
n/a

Start by locating the Documents editor entry point and reviewing how narrative text is edited. Define the assistant's supported drafting, rewriting, tone, and grammar flows, then verify that each requested operation works directly in a Document.

Written by the indexing model from the issue text.