The previous hero-banner was composed as a wide banner with an empty left
40% reserved for overlay text. In the 50/50 hero column it rendered as a
shrunken half-width picture with dead space on both sides.
New illustration fills the whole 16:9 frame edge to edge (code/CI/CD left,
container + host cluster centre, observability right) so the right hero
column reads as a system diagram at its native 518px width, with the
2048w lightbox for detail reading.
Also add a 1280w WebP so DPR2 desktops do not pull the 2048w asset on
first paint.
