setReservedHeight method
Records the height of the chrome reserved above the time grid besides the date row — the all-day band (#48). Recomputes the scroll clamp so the grid viewport excludes the band. A no-op when the height is unchanged.
Implementation
void setReservedHeight(double height) {
if (height == _reservedHeight) return;
_reservedHeight = height;
_calculateOffsets();
}