This fixes an issue where, if line numbers are turned off in a code
block, focusing on an empty line would cause the text cursor to be
hidden.
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## Summary by CodeRabbit
- **Style**
- Updated code block layout to improve appearance when line numbers are
disabled.
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Co-authored-by: L-Sun <zover.v@gmail.com>
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## Summary by CodeRabbit
- **New Features**
- Added a toggle in the code block toolbar to show or hide line numbers for individual code blocks.
- The display of line numbers now respects both global and per-block settings, allowing more flexible control.
- **Style**
- Updated styles to hide line numbers when disabled via the new toggle option.
- **Tests**
- Added end-to-end tests to verify toggling line numbers visibility and undo/redo behavior.
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<!-- This is an auto-generated comment: release notes by coderabbit.ai -->
## Summary by CodeRabbit
- **New Features**
- Updated the code block toolbar to use a toggle switch for the "wrap" option, providing a more interactive user experience.
- **Style**
- Adjusted the height of the language selection button for consistent appearance.
- Refined code block container padding and increased spacing for line numbers to improve readability.
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<!-- This is an auto-generated comment: release notes by coderabbit.ai -->
## Summary by CodeRabbit
- **New Features**
- Introduced a preview mode for code blocks, allowing users to toggle between code and rendered previews (e.g., HTML output) directly within the editor.
- Added a preview toggle button to the code block toolbar for supported languages.
- Enabled dynamic rendering of code block previews using a shared WebContainer, allowing live HTML previews in an embedded iframe.
- Added HTML preview support with loading and error states for enhanced user feedback.
- Integrated the preview feature as a view extension provider for seamless framework support.
- **Bug Fixes**
- Improved toolbar layout and button alignment for a cleaner user interface.
- **Tests**
- Added end-to-end tests to verify the new code block preview functionality and language switching behavior.
- **Chores**
- Updated development server configuration to include enhanced security headers.
- Added a new runtime dependency for WebContainer support.
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L-Sun
