This PR fixes#14040
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## Summary by CodeRabbit
* **New Features**
* Code blocks can be collapsed and expanded via a toolbar toggle
(visible when the document is editable).
* Collapsed code blocks show a limited preview (~8 lines) with a bottom
fade overlay and reduced padding.
* Toolbar button updates icon and tooltip to reflect collapsed/expanded
state.
* Collapse state is preserved on the block so its current
collapsed/expanded setting is retained.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->
fix#14269fix#13920fix#13977fix#13953fix#13895fix#13905fix#14136fix#14357fix#14491
#### PR Dependency Tree
* **PR #14498** 👈
This tree was auto-generated by
[Charcoal](https://github.com/danerwilliams/charcoal)
<!-- This is an auto-generated comment: release notes by coderabbit.ai
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## Summary by CodeRabbit
* **Bug Fixes**
* Callout and toolbar defaults now reliably show grey backgrounds
* Keyboard shortcuts behave better across layouts and non-ASCII input
* Deleted workspaces no longer appear in local listings
* **New Features**
* Cell editing now respects pre-entry validation hooks
* Scrollbars use themeable variables and include Chromium compatibility
fixes
* **Style**
* Minor UI color adjustment for hidden properties
* **Tests**
* Added unit tests for table column handling and keymap behavior
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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.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->
---------
Co-authored-by: L-Sun <zover.v@gmail.com>
<!-- This is an auto-generated comment: release notes by coderabbit.ai -->
## 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.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->
<!-- 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.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->
<!-- 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.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->
Ahsan Khaleeq
