500 rps failed the capacity gate every night (peach mix is write-heavy; the
write path is structurally capped on 3-node RF3 full placement). A settled-
cluster capacity sweep measured the mix clean (0.00% error, 0 follower
restarts) at 100/150/200/250 rps; set the nightly target to 200 rps with margin
for a 1h x 30-night endurance run. SLO gates unchanged.
Also fix the image drift: the manifest pinned stress:m12-soak-eval (never
pushed -> ImagePull NotFound), while the live cronjob already ran the pullable
stress:m12-rc7-seedretry. The manifest now matches the live, pullable image.