v4.2.2

The runtime application is unchanged from v4.2.1. The image declares a
HEALTHCHECK on /api/version, which the bootloader reads off Docker's events
stream as its primary health signal -- the reason this is a new version
rather than a rebuild.

Ships the RTOP-283 work: a bootloader on port 8445 that supervises the
runtime container and can change its version from the editor without SSH,
a one-line container install with uninstall, and CI that runs on pull
requests. Also publishes bootloader-v1.0.0, which has never been built.