Wrapping of "$___" is inconsistent with browser

[rf-]

I noticed a case where Pretext's wrapping is inconsistent with browser behavior: https://codepen.io/editor/rf3521dcb4b0/pen/019d55dd-d8c4-750a-8b92-cd8d69641e0b

This repro uses prepareWithSegments/layoutWithLines, although I originally saw it using the inline flow API.

[soonxf]

me to

bug

[ImpulseB23]

gotchu #105