KetraTermWRAP_PADDING
Artificial final-column blank inserted when a width-2 glyph moves to the next physical row. Valid only with EMPTY, at the last column of a row whose TerminalRenderFrame.lineWrapped is true.
Logical text extraction omits this cell when joining soft-wrapped rows; ordinary empty cells still represent spaces within a logical line. Rendering and rectangular selection retain its physical cell geometry.