Context: Plan B (https://gist.github.com/vjt/48a75dc067f27108e4261d4c7380e00d) had each testnet container build: from source on first docker compose up (peak RAM ~200–300 MB for autoconf+gcc, too much for a 256 MB box). Hypnotize picked GHCR as hosting; this delta wires the push into the two existing CIs and flips the compose to image:.
Scope: minimal. One new step per CI workflow, compose switches to published images, first up becomes a pull instead of a compile.