This PR implements [feature request] #14845
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## Summary by CodeRabbit
* **New Features**
* Add-block control that appears when hovering blocks in page mode to
insert and auto-focus a new paragraph; control hides after insertion.
* **Improvements**
* Improved hover and interaction handling to avoid accidental triggers
when interacting with the drag handle or add-block control.
* Consistent sizing, positioning, and visibility behavior for the
add-block control.
* **Style**
* Moved heading icon slightly for improved visual alignment.
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Co-authored-by: DarkSky <25152247+darkskygit@users.noreply.github.com>
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.
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This PR fixes#14874
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## Summary by CodeRabbit
## Release Notes
* **Bug Fixes**
* Removed height limitation on Mermaid diagram previews in code blocks,
allowing larger diagrams to render at their full size without being
constrained by a fixed maximum height.
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Bug Resolved
#14795
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## Summary by CodeRabbit
* **Bug Fixes**
* Made row and column sorting deterministic when items share the same
order value, reducing unexpected cell shifts.
* Adjusted comparator behavior to preserve tied-order grouping, which
may change displayed column/row sequence in edge cases.
* Improved consistency of table rendering and cell placement across
refreshes and edits.
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This PR fixes#14755 bug
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## Summary by CodeRabbit
* **Bug Fixes**
* Fixed keyboard shortcut handling to properly distinguish between
locale input characters and actual shortcuts when using Alt+Meta key
combinations.
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