Keep list item color after outdent

[JiuqingSong]

<ol style="margin-top: 0px; margin-bottom: 0px; list-style-type: decimal;" data-editing-info="{&quot;applyListStyleFromLevel&quot;:false,&quot;orderedStyleType&quot;:1}" start="1"><li style="font-family: Corbel, Skia, sans-serif; font-size: 12pt; color: rgb(12, 100, 192);"><div role="presentation" class="elementToProof">Aaaa</div></li><ol style="margin-top: 0px; margin-bottom: 0px; list-style-type: lower-alpha;" data-editing-info="{&quot;applyListStyleFromLevel&quot;:true}" start="1"><li style="font-family: Corbel, Skia, sans-serif; font-size: 12pt; color: rgb(12, 100, 192);"><div role="presentation">bb</div></li></ol></ol><!--{"type":"range","start":[0,1,0,0,0,0],"end":[0,1,0,0,0,0],"isReverted":false,"isDarkMode":false}-->

Press Backspack key, expect the list item number "2" should keep the same color.

Before:

After:

[Copilot]

Pull request overview

This PR fixes a bug where list item color formatting was lost when outdenting a list item (pressing Backspace). The fix ensures that segment-level formatting (like text color) is preserved by using the formatHolder.format property instead of the list item's format property when creating a new list item during the outdent operation.

• Changed deleteList.ts to pass formatHolder.format instead of format when creating a new outdented list item
• Added comprehensive test case to verify format preservation during list outdent operation

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
packages/roosterjs-content-model-plugins/lib/edit/deleteSteps/deleteList.ts	Fixed the format parameter in createListItem call to use formatHolder.format instead of format to preserve text color and other segment-level formatting during outdent
packages/roosterjs-content-model-plugins/test/edit/deleteSteps/deleteListTest.ts	Added test case verifying that list item format (specifically textColor) is preserved in both the original and newly created list items after outdenting

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