Text editor moves a paragraph after a nested task item into that item #3624

Initial Checklist

• I understand this is a bug report and questions should be posted in the Community Discussions
• I searched issues and couldn’t find anything (or linked relevant results below)

Bug Description

The markdown round trip of the text editor moves a paragraph that belongs to a task item into the nested task item above it. Follow-up to #3583.

Reproduction Steps

Open this file in the text editor, save, reload.

- [ ] a
  - [ ] b

   x c
- [ ] d

x c is indented 3 spaces: past the content column of a (2), but short of the content column of b (4).

Expected Outcome

x c stays a second paragraph of task a, as in CommonMark.

Actual Outcome

• On main the first letter is lost and the rest moves into b: - [ ] a\n - [ ] b\n \n c\n- [ ] d.
• With fix(editor): keep task list content and indented code fences in markdown #3616 the text is kept, but x c is still parsed into b and saved as - [ ] a\n - [ ] b\n \n x c\n- [ ] d. The workaround in markdownTaskList.ts attaches a line to the deepest item whose marker is indented less than the line, instead of the deepest item whose content column the line reaches.

The same paragraph indented 2 spaces works.