Two adjacent backdrop-filter elements (nav at y=0-80, filter at y=80+)
always show a visible seam at their boundary because each filter clips
its own blur kernel, so the edge pixels sample slightly different
neighborhoods. Same recipe doesn't help — it's a structural issue.
Fix: when filter is stuck, render an absolutely-positioned glass child
inside the filter that extends from -top-20 to bottom-0 (i.e. covers
nav area + filter area as ONE element). Nav reads filterStuck from a
tiny shared zustand UI store and disables its own glass layer in that
state, so only the shared band is visible. Single element, single
backdrop-filter, no seam.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
