An image with a side above the deployed routes' 2000px many-image bound
could be durably committed by read_image, ride every later request, and
permanently fail the session with provider 400s. Admission now enforces a
configurable maxImageDimension (default 2000) during the full decode, so
read_image surfaces a recoverable tool error naming the limit instead of
poisoning durable history; the Web composer gets dedicated copy for the
new IMAGE_DIMENSION_TOO_LARGE reason.
Fixes#2626
creatixchu
0e39055121