Peritext bugs

[streamich]

• When selecting across multiple paragraphs. Reports "Encountered two children with the same key, 123."
• Select range, assign italic formatting, press Right arrow, now text until end of paragraph is selected.
• When deleting whole inline annotation, it gets into a state where it has not content, but is rendered on the screen and it is not possible to add text to it. To reproduce: select range, annotate as inline code, press delete to delete the whole text contents, but the inline code annotation remains.