Move the display and button panels into a single wrapper and rely on
viewport-height sizing with hidden page overflow to keep the calculator
contained. Also trim redundant panel-specific layout rules and styling.
Remove layered shadows and pressed-state transforms from the calculator UI, and update the stack copy icon markup and active feedback to match the new flat design.
Remove the responsive two-column desktop arrangement and make the calculator stack vertically with a 4-column display button row that preserves alignment. Also align the display buttons with the shared base button styling.
Wrap the display controls in a dedicated grid container, add a spacer for the missing cell, and simplify the button styling so the layout stays consistent across sizes.
Wrap the display and control buttons in a shared display block so the
stack and button panels align as a single unit. Reduce corner radii and
adjust gaps/padding across the calculator to better fit the updated
portrait and desktop layouts.