mesh/merge-gate pass: builds mesh-host → ace, g14, novox, shanks; no bus step; every machine composes with the change as it did without (4 of 4 compose)
Third review of mesh-catalog #147.
A unit's name can now come from a setting (a template's instance), so every systemctl call that names a
unit passes `--` before it, and a name can never be read as an option.
On removal, a unit is started or enabled again only when it is exactly the stopped and disabled the mesh
held it to. A masked unit, or one somebody started or enabled since, is left as it is, and the report
says why. A restore that fails (the start refused, or the unit not running after it) puts back what this
attempt changed and is reported as waiting, so no apply is made fatal by it and the next one tries again.
The tests' fake service managers read systemctl's arguments in the shape they were written for
(oldShape); internal/system's own test holds the `--`.
