Support prebuilt airplanes.live images in update and runtime scripts #16

Job	Run time
bats	28s
image rootfs smoke	37s
shellcheck + bash -n	20s
installer smoke (ubuntu:24.04, bundled)	52s
installer smoke (debian:13-slim, standalone)	50s
installer smoke (debian:13-slim, bundled)	44s
installer smoke (ubuntu:24.04, standalone)	1m 3s
	4m 54s

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