Pasting a new line causes incorrect cursor movement

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### Bug report

Hi,

There is a strange behavior in the current 4.18.0 version. It is easily reproducible on the docs [website](https://commerce.nearform.com/open-source/react-live):

1. Copy a piece of code with a new line in it
2. Paste it somewhere in the editor several times in a row
3. See the cursor moves forward and breaks the code eventually

https://github.com/user-attachments/assets/8acc39af-7a63-4dea-9310-34d0774cf8f7

Reproduce the issue on the linked React Live docs website by repeatedly pasting code containing a newline. Trace the editor's paste and cursor-position handling, then verify that repeated multiline pastes leave the cursor in the correct position and do not corrupt the code.

Written by the indexing model from the issue text.