Cursor Up: Cursor moves to incorrect thought after New Thought Above

[raineorshine]

Steps to Reproduce

- a
  - b
    - =pin
    - b1
  - c

1. Set the cursor on b1
2. New Thought Above (Shift + Enter)
3. Set the cursor on c
4. Cursor Up (ArrowUp)

Current Behavior

The cursor moves to the new thought.

Expected Behavior

The cursor should move to b1.

Cursor Up should always move to the visible thought immediately above the cursor thought, regardless of hierarchy.

Testing

Add a test to https://github.com/cybersemics/em/blob/128153531a41c49eb19daf7eb784a40f768a1020/src/actions/__tests__/cursorUp.ts.