The --macro dispatch arm now opens the top-level agent bracket before
macro_execute and closes it signal-aware afterwards, draining pending
hooks like the --execute arm; both bracket calls no-op without a loaded
agent, so agent-less macro runs are unaffected. The isolated arm of
macro_execute closes the bracket an in-macro .agent step opens on its
fresh context, on the step-failure path too. Binary-level tests pin
agent.started plus exactly one terminal event for the --agent flag and
for in-macro .agent steps in both isolation modes, on success and
failure.
