Cells could only enter edit mode via double-click or a physical keyboard,
so touch devices had no way to edit a cell. Treat a touch/pen tap as the
edit gesture, distinguishing a tap from a scroll by movement and branching
per pointer type so mouse double-click stays unchanged. Also reveal the
row expand button on hover-less devices so the row detail view stays
reachable.
The New row control is a role=button div with no keydown handler, so Enter/Space never triggered it. It also lives inside the grid element, whose native keydown listener caught the Enter and ran cell navigation against the previously focused cell.
Add Enter/Space activation to the button, and make the grid keyboard handler ignore keydowns that originate from a focusable child rather than the grid element itself, so in-grid controls handle their own keys.
The focus ring is gated on the grid having DOM focus (.bodyGrid:focus .cellFocused), but the focusedCell atom is never cleared when the grid blurs. Clicking outside hides the ring via the :focus gate while the atom still points at the old cell.
Selection was committed on click (mouseup), while the grid receives focus on mousedown. Clicking a new cell re-focused the grid before the atom updated, briefly painting the ring on the previously selected cell. Commit selection on mousedown so the atom updates in the same event that grants focus, before the browser paints.
Philipinho