The release directory under /home/sam/deployment/resume is the rollback unit;
deploy.sh stages releases/<timestamp>-<sha>/, flips `current` atomically,
builds the image from that directory and gates on /healthz, restoring the
previous release on any failure.
The rehearsal recipe in the header is kept as comments only; the pasted spec
lost the comment prefixes on the multi-line printf, which would have made the
script exit 1 on startup. It now uses \n escapes on one commented line.
