Stage reads a specific host path. Use an absolute path; the
sandbox binds it at the same location inside the sandbox (via
a read-only bind mount). Multiple read paths are declared as
separate FsRead entries — one per path.
from_effects on the isolation policy turns each FsRead(p)
into a RoBind { host: p, sandbox: p }.
Stage writes to a specific host path. Use an absolute path;
the sandbox binds it RW at the same location inside. This is
a deliberate trust widening — the sandbox cannot validate
whether binding (say) /home/user RW is sensible. Callers
that need this are declaring the trust decision explicitly
via this effect.
from_effects on the isolation policy turns each FsWrite(p)
into an RwBind { host: p, sandbox: p }.