nobody_else_and_nothing_else_answers_it read five replies after
waiting only for the first, so it failed whenever the other four were
not posted yet. It failed once in a full `make gate` run, when many
test binaries ran at once. The helper now waits for as many posts as
the test reads.
The M4b plan's copy is left as it was handed over.
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>