Do not add undo snapshot from ImageEdit plugin if image is not changed

[JiuqingSong]

1. Add a new property skipUndo in ContentChangedEvent
2. When this property is true, UndoPlugin will not add undo snapshot / set has new content for this event
3. When ContentChangedEvent is triggered due to the following reasons, set this property to true
   • Switch color mode
   • Keyboard input (to follow the existing behavior)
4. When add image editing border, set this property to true, so no need to add undo snapshot for image editing border
5. When remove image editing border, check if image is edited since current border is added. If not, do not add undo snapshot

[Copilot]

Pull Request Overview

This PR adds a new skipUndo property to ContentChangedEvent to provide granular control over when undo snapshots are added. It optimizes the ImageEdit plugin to only create undo snapshots when actual image modifications occur, not for temporary UI states like showing/hiding edit borders.

• Add skipUndo property to ContentChangedEvent interface for controlling undo snapshot creation
• Refactor UndoPlugin to use the new skipUndo flag instead of hardcoded source checks
• Optimize ImageEdit plugin to track initial state and conditionally skip undo snapshots for border operations

Reviewed Changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
ContentChangedEvent.ts	Add optional skipUndo property to event interface
checkEditInfoState.ts	Fix comparison logic for rotation values to compare with initial state
ImageEditPlugin.ts	Track initial editing state and conditionally skip undo snapshots
EditorTest.ts	Update tests to include skipUndo property in expected events
UndoPluginTest.ts	Refactor tests to use generic skipUndo flag instead of specific sources
formatContentModelTest.ts	Update tests with skipUndo expectations for comprehensive coverage
Editor.ts	Set skipUndo: true for color mode switching events
UndoPlugin.ts	Simplify logic to use skipUndo flag instead of hardcoded source checks
formatContentModel.ts	Set skipUndo based on snapshot conditions and keyboard source
insertLinkTest.ts	Add missing skipUndo property to test expectations

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