Sticky header for markdown/Rich text editor
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When the user scrolls the toolbar out of view while editing, make the toolbar header sticky.
Updated 2025-08-27:
### Problem Statement
Following the recent improvement where the [editor expands based on content length ](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/197700)(removing the internal scroll), users editing long content face a usability issue: when working at the bottom of lengthy content, they must scroll all the way back to the top to access the editor toolbar.
This creates friction in the editing workflow, particularly for:
* Long documentation pages
* Detailed issue descriptions
* Extensive merge request descriptions
* Wiki pages with substantial content
| Current state |
|---------------|
|  |
### Current Behavior
1. Editor expands to show full content (no internal scroll)
2. Editor toolbar remains fixed at the top of the editor
3. When editing content at the bottom of a long document, users must:
* Scroll up to access formatting options
* Lose their place in the document
* Scroll back down to continue editing
### Proposed Solution
Implement a sticky positioning for the editor toolbar that remains visible and accessible as users scroll through the content.
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Feedback from 1:1 sessions with @jmandell
issue