[Jul 7] Active element, bridge strips, subtractive B, refusal mark. Active element visual: dashed line in selection color, sized per-edge. Retired active_color/active_width (separate controls gone — the mark is just a selection-colored dash now). Dashes centered on grid points for symmetric inked corners. Fixed a freeze bug. Bridge strips: identity rule replaces the old monotone gate. Consume a wall exactly when it IS what the grid builder would build there — every interior rail vert must lie ON the straight a→b chord, strictly advancing. Disambiguates topology's blind spots (wedge case, blown-lid bug). Bent walls correctly classify bare/double-wall. One-region B (subtractive delete + heal ladder): single selected region → delete region (rim kept) → heal the hole. Heal dispatch: planar rim → grid fill; non-planar + carve's sigma → mirror heal; else grid-fill fold search (scored by quad planarity); else honest n-gon cap. Heal faces stamp active material. Documented in subtractive-b.md. Refusal mark: refused ops flash a hollow ink X in the viewport corner, stroked with the ink pen. No text.