Seed the eleven node seats with the verbs they start with. A provision may
have the machine's reach: a requirement for it resolves only to a provider
in the node's own set, is never pulled in, and is refused naming who could.
A shell contribution's for gains xinitrc and xresources, placed only by the
holder of node-display-server.
A module contributes environment variables, PATH entries and shell code in named slots;
the holder of the matching seat places them with ${environment:posix|systemd} and
${shell:<shell>:<slot>}. Rendered in module order with a naming line per contribution,
PATH entries added only when missing, machine facts resolved first. A variable two
modules set, or a placeholder outside its seat's holder, is refused at parse (the
catalogue check) and at composition. Filled after every other placeholder pass, so no
scanner ever reads a shell's own ${...}.
jochen