- docs/window-curvature.md holds the full contract (now also: the next
press starts at 1x, return values, a drag keeps its value, neither side
restores the other's state); the patch headers of window-curvature and
frame-controls point to it and keep only their own side.
- frame-controls header: the localStorage history points to
docs/ui-patches.md#persistent-state.
Comments only, no VERSION bumps.