Merge nucleic/rustic-north-robin-niry into main

Mirrored from corpo 52e4273.

src/pages/index.astro

@@ -215,6 +215,20 @@ const canonical = new URL('/', Astro.site);
        it falls back to body, and a transparent answer from this layer hands the
        toolbar its default grey instead of the page's own dark. */
     background-color: var(--paper);
+    /* The apron. A deep rubber-band fling drags this layer's edges into view, and
+       what Safari composites beyond them is not reliably the page's to choose: the
+       gap fill has its own rules, and on a hard fling the fixed layer is repositioned
+       asynchronously and can lag the bounce by whole frames — which put a strip of
+       not-this-layer on screen at exactly the moment the eye is on the edge. Coverage
+       has to travel with the layer itself, so it is cast from it: a zero-blur shadow,
+       one viewport of solid --paper beyond every edge, clipped by nothing (shadows
+       paint outside the border box and ignore this element's own overflow). Invisible
+       at rest, it means any strip revealed next to this layer during any bounce, at
+       any lag, in either direction, is the same paint as the layer's own faded edge.
+       The lvh spread matters: the bounce can't exceed a viewport, so the apron always
+       outruns it. Plain vh first as the fallback for engines without lvh. */
+    box-shadow: 0 0 0 100vh var(--paper);
+    box-shadow: 0 0 0 100lvh var(--paper);
   }
 
   /* The grey bar, properly.