PR review (comment 17358) found a real gap via mutation testing: replacing
the "pid never found" warn with die "no process appeared" left the whole
suite green, because neither existing test drove the case the fall-through
exists for -- running_pid() never finds anything (as its own doc comment
says it eventually will) while /healthz answers anyway.
Adds test_await_daemon_started_pid_never_found_but_healthy_warns_and_survives:
running_pid always empty, poll_health_body succeeds. Asserts DIED_CALLED=0,
the warn line is emitted, and NEW_PID stays empty (the honest "could not
establish this" answer, never a guessed pid).
Verified both halves myself: reverting the warn to die "no process appeared"
turns this one test red (FAIL: await_daemon_started must not die...);
restoring it returns the suite to green.
Dai Ha
856dfc6318