Updates the Explorer feature preview copy to explain the SQL Editor
transition, Notebooks, and Snippet migration plans. Adds feedback
questions and moves the preview image above the content.
Validation: Prettier and `git diff --check` passed.
<!-- This is an auto-generated comment: release notes by coderabbit.ai
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## Summary by CodeRabbit
- **Documentation**
- Updated the Explorer preview layout by moving the preview image below
the introductory text.
- Replaced feedback questions with a clear overview of what enabling the
preview provides, including SQL Editor replacement and Notebooks
management through the dashboard and Assistant.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->
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Co-authored-by: Joshen Lim <joshenlimek@gmail.com>
## Context
Sets up the Explorer behind the feature preview modal + removes the
temporary entry point from the SQL Editor
Changes are still not live on production, so will only affect local +
staging.
Enabling the feature preview will replace the sidebar nav for SQL Editor
to new Explorer (Icon remains unchanged, just the label)
<img width="918" height="647" alt="image"
src="https://github.com/user-attachments/assets/b088eb47-1176-4618-b345-d1ec0521b092"
/>
<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit
- **New Features**
- Added an “Explorer & Notebooks” feature preview with an overview image
and direct access to Explorer or SQL Editor.
- Added Explorer navigation when the preview is enabled.
- **Improvements**
- Updated desktop and mobile navigation to consistently display the
available editor destination.
- Improved the Explorer shortcut tooltip to clearly say “Go to
Explorer.”
- Organized SQL Editor previews under the Editors category.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->
