Joins the CI-regressed sim-bench sweep (S7 style: threshold const with
budget+slack rationale, cfg(sim-bench) test, --test-threads=1 job).
Drives the real trunk WS route through the PRODUCTION serve path
(rutster::serve::serve_with_nodelay) over a real loopback socket at the
real 20ms cadence. Healthy ~1-2ms; a Nagle regression stalls ~40ms+;
threshold 20ms splits the regimes by an order of magnitude each way.
Verified load-bearing: fails when tcp_nodelay(false) — see module doc
for the Option D socket2 TCP_QUICKACK suppression that defeats the
Linux loopback's quick-ACK heuristic so the assertion actually
catches the Nagle regression on this runner.
Signed-off-by: Aaron D. Lee <himself@adlee.work>
