The fade-to-transparent was invisible: the row sits on the same pale
canvas, so masking the edge to transparent just revealed more of the
same colour (and often landed on an inter-chip gap). Replace it with a
surface-coloured scrim the chips slide under, topped by an outward
chevron, shown only on an edge with more content. RTL-mirrored.
Chips clipped at the viewport edge with no cue that more filters exist.
New reusable EdgeFade widget (ShaderMask + dstIn) fades an edge only
while content remains beyond it, driven by scroll metrics; RTL mirrors
via Directionality. Applied to the inventory filter bar, market filter
bar and calendar month strip.
