Set the app-wide space-driven density policy for the classic
<cngx-stepper> strip. 'auto' degrades labels on the strip's own
container width (full -> compact -> minimal); 'comfortable'
(library default) keeps full labels at every width. The optional
second argument overrides the per-step px thresholds (default
STEPPER_DEFAULT_DENSITY_BREAKPOINTS). Orthogonal to the
mobileCollapse axis; the Material twin ignores this setting.