Multi-line bullet list creation causes list splitting and item duplication

[mdeclercq]

Describe the bug
When creating a bullet list from a multi-line text selection, adding items manually to the list creates multiple lists and generates duplicate list items.

Git bisect shows this issue was introduced in commit c4aa81 (release v9.44.0).

To Reproduce

1. Go to the Rooster demo: https://microsoft.github.io/roosterjs
2. Input 2 lines of text in the editor

line 1
line 2

3. Select all the text and click on the bullet list icon
4. Focus the end of line 2
5. Add a new line by pressing Enter
6. Type line 3
7. Notice that 2 separate ul list elements are created, one containing line 1 and another one containing line 2 and line 3
8. Press Enter again, the list item line 3 gets duplicated

Expected behavior

• A single ul list remains containing 3 items li
• List items are not duplicated when pressing enter

Screenshots

Device Information

• OS: MacOS 26.1
• Browser : Chrome 143.0.7499.170

Additional context

Screen.Recording.2026-02-06.at.10.07.28.mov