v1.4.7

Same agent code as 1.4.6, which was tagged but never produced a binary: the
build broke on the day Debian 11 went end-of-life. 1.4.6 has no release
assets; use this one.

Fixed

• The build image could no longer be built. bullseye-security's Release
  file passed its Valid-Until when Debian 11 reached end of life, and apt
  refuses the entire update over it. Only the freshness check is relaxed -
  signatures are still verified - because the alternative, moving to
  bookworm, raises the glibc floor from 2.31 to 2.36 and would kill the
  binary on the older boxes this base exists to support.
• packaging/build.sh built the image with -q and its output redirected to
  /dev/null, so the failure above reached CI as a bare "exit code: 100"
  with nothing else. It now stays quiet on success and prints the docker
  output on failure.