Add responsiveLayout "collapseEditable" so folded cells stay editable

[EmpiDev]

Closes #3749. Follows the direction from the #3875 review.

responsiveLayout: "collapse" builds its block from a mock cell component whose
getElement() returns a throwaway div. The editor, validators and cell events are
all bound to the real cell element at cell-init, so none of them reach that copy
and a folded field is read only.

This adds a sibling mode, "collapseEditable", that relocates the real cells into
the row's existing .tabulator-responsive-collapse container instead:

• showColumn puts a relocated cell back in the row, at its column's position,
  before the column is made visible again.
• generateCollapsedRowContent restores before it tears down, so a rebuild moves
  cells rather than orphaning them; one landing mid-edit is deferred and replayed
  on edit-editor-clear.
• The toggle formatter dispatches row-responsive-toggled, so an editor left in a
  collapsing container gets closed.

The row stays display: block, and the labels stay real elements, in place during
the edit. No changes to Edit, Validate, Cell, Row or any renderer: the
validation chain, cell.setValue and cellEdited work because it is the same
cell. "collapse" is untouched.

28 jest specs and 11 playwright specs for what jsdom cannot measure.