The rule was right about data and wrong about everything else. The
builder mounts the container runtime's socket, which is not its data,
does not belong to it, and must not be declared as one of its
directories — and the check refused the builder's own manifest.
Caught by the lab, though not honestly: the run was already going when
this went in, so the builder binary was rebuilt mid-run with the check
compiled into it and the failure was mine, not the mesh's. Confirmed
against the manifest directly rather than inferred from the log.
What it was protecting is real and stands — the fourteen mounts are all
declared. But enforcing it needs a way to tell "the directory my data
lives in" from "a machine facility I was granted", and the mesh has no
vocabulary for the second. `capabilities` is the closest thing and does
not name paths. That is a design decision, so it goes back to
04-ISSUES/026 rather than being invented here to make a check pass.
The check that every real manifest still parses is kept. It costs
nothing and it is how the next attempt at this finds out sooner.