Out-of-process modules timed out with "did not report ready within 45s"
because apply_sandbox never allowed the child to reach breadd's Unix
socket. Path-based AF_UNIX connect is mediated as filesystem access, so
without a rule for the socket (and its parent) UnixStream::connect failed
with EACCES and the hello handshake never completed.
Pass socket_path into apply_sandbox and add baseline ReadDir/ReadFile
rules for the socket directory and path, matching the existing module-
directory grant. Update unit-test call sites accordingly.
