Formula interactions/improvements

[luke-quadratic]

[Unscoped, this issue is purely for tracking Formulas related features, when worth prioritizing we'll break individual pieces out into separate issues and scope properly]

Minor formula interactions that differ from familiar mainstream spreadsheets that are worth considering (ongoing list):

• From user reviews we've heard many times a permanent Formula bar is a sufficient experience to inline only
• Arrow keys up and down when on the exterior of a Formula navigate to the end/beginning of the formula; in Quadratic they navigate you out of the cell in most cases
• List of related Formulas progressively turns into the exact Formula chosen with the hints for what should be in that formula; in Quadratic we offer a much less legible experience