fix(editor): transcript note will create useless docs (#14976)

fix #13520


#### PR Dependency Tree


* **PR #14976** 👈

This tree was auto-generated by
[Charcoal](https://github.com/danerwilliams/charcoal)

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## Summary by CodeRabbit

* **Tests**
* Added comprehensive test coverage for markdown insertion functionality
to verify that existing document metadata remains unchanged when
importing markdown content into workspace documents.

* **Chores**
* Optimized internal markdown-to-snapshot conversion process to use a
more direct and efficient conversion approach.

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