ConstThe bar is fx and the editor, with the expand chevron inside the field at its right edge.
Under it, the MobileInputToolbar: the letters, numbers and date inputs, Tab, Enter, and
cancel / commit. There is no name box and no Calculate Now button; the commands behind them stay
reachable elsewhere. Expanding grows the field upward: the bar is a flex sibling below the grid,
so the grid gives up the lines.
It drives the same shared SheetEditable as the grid through useFormulaBarSession: a tap on the field starts the edit on the active cell, and a tap on a cell while editing inserts a reference, exactly as the desktop bar does. Enter and Tab (the toolbar's, the keyboard's) commit, move the active cell and open the next cell for typing without dropping the keyboard; cancel and commit end the entry and hand focus back to the grid.
The formula bar for a touch-only device: the same input the in-grid editor renders, in a box built for the bottom of a phone screen, with a row of entry buttons under it.