[Table Improvements] Add undoSnapshot when tab on a table cell

[juliaroldi]

Add undoSnapshot after pressing Tab key in a table that has new content, otherwise if the user type content in a table and press tab to move to another cell and then undo the content, all the typed content will be removed.
Before:

After:

[Copilot]

Pull request overview

This pull request fixes an undo functionality issue where typing content in a table cell and pressing Tab to move to another cell would result in losing all typed content when undoing. The fix adds an undo snapshot when Tab is pressed in a table cell with new content.

Changes:

• Added Tab key handling logic to create undo snapshots when tabbing between table cells with new content
• Implemented a helper method to detect if the current selection is inside a table cell
• Added comprehensive test coverage for the new Tab key behavior

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
packages/roosterjs-content-model-core/lib/corePlugin/undo/UndoPlugin.ts	Added Tab key handling in onKeyDown method and implemented isInsideTableCell helper method to check if selection is within a table cell
packages/roosterjs-content-model-core/test/corePlugin/undo/UndoPluginTest.ts	Added 5 comprehensive test cases covering various scenarios for Tab key behavior in and out of table cells

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[Copilot]

The optional chaining on selection?.range.collapsed is redundant. Once you've verified that selection?.type == 'range', the selection is guaranteed to be non-null, so you can safely access selection.range.collapsed without the optional chaining operator.

Suggested change

	if (selection?.type == 'range' && selection?.range.collapsed) {
	if (selection?.type == 'range' && selection.range.collapsed) {

[Copilot]

For better type safety and clarity, explicitly convert the return value to a boolean. The current code returns the HTMLElement or null/undefined from findClosestElementAncestor, which works in a boolean context but makes the return type less clear. Consider using double negation (!!) or checking !== null to ensure a boolean return type.

Suggested change

	return editor.getDOMHelper().findClosestElementAncestor(startContainer, 'td, th');
	return !!editor.getDOMHelper().findClosestElementAncestor(startContainer, 'td, th');