Tests that read ../../../mesh-catalog or ../../../mesh-host gave a verdict
that depended on what sat beside the checkout: a stale or dirty sibling
failed them on a desktop, and a missing one skipped them unseen. They now
read the clone the build seat puts in MESH_CHECK_BESIDE, failing when it is
absent there, and elsewhere a copy captured at a named commit.
The skip had hidden that the builder test read a module retired by ADR 0190.
The systemd reading test no longer counts the machine's own environment.d.
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 ${...}.
jschoubben
jochen