v0.6.19

kern 0.6.19

Docker compose parity for web stacks, plus the defects that running the work
on real hardware exposed.

Added
  - docker / docker-compose shim: invoked under either name, kern translates
    the argv and runs an existing script unchanged. Every flag is forwarded,
    dropped as a no-op, or refused by name. There is no fourth bucket where a
    flag is silently ignored.
  - kern compose, ten verbs over a docker-compose.yml or a kern profile.
  - kern compose <file> systemd: prints a unit, installs nothing, and says in
    its own comments that it does not supervise.
  - port: and Docker's expose:, declaring the port a service listens on inside
    the pod. kern reserves it and passes port: as PORT.

Fixed
  - kern stop waited the full grace period for a signal the box could not
    receive: 9013 ms to stop one box. It now reads SigCgt and skips the
    graceful phase when the init provably cannot catch the signal (4 ms), while
    a service that does trap it still gets its full grace.
  - kern stop --all deleted systemd unit files it had never written.
  - compose config reported as clean a stack that up refused.
  - docker compose up -d died on kern's usage text.
  - The /dev/shm change from 0.6.19-pre is reverted: the leak it fixed does not
    exist. The evidence was an echo after a semicolon, which runs whatever the
    command before it did. Measuring the pre-fix binary showed the cap holding
    all along.

636 Rust tests, 61 Python, 50 Node. clippy clean. Verified on x86_64 plus the
Pi 5, Jetson Orin Nano and Arduino UNO Q.