Jitter buffer v2, per-minute rx logging, websocket keepalive

The cohost sounded jittery on the 2026-11-03 show. v1 skipped ahead on an
underrun and kept playing from an empty buffer, so after the first hiccup
every later wobble was another glitch. It also never corrected a slow guest
clock: ~12 glitches/min in simulation at 30 ppm slow.

- Underrun: hold the sequence position and refill to a larger target
- Drift correction both ways (drop/insert a frame in quiet moments),
  quiet judged relative to the guest's own noise floor
- 80 ms start, 300 ms max, relaxes after 2 calm minutes
- Log 'rx 1m:' stats, the selected route, and call totals
- Ping the guest websocket every 25 s (the proxy closed it every 90 s)
- Simulation kept in test/jb_sim_test.go.txt

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

web/static/host.js

@@ -39,7 +39,7 @@ function render(s){
     $('#dIn').textContent = Math.max(-60, setMeter($('#mIn'), c.inPeak)).toFixed(0) + ' dB';
     $('#dOut').textContent = Math.max(-60, setMeter($('#mOut'), c.outPeak)).toFixed(0) + ' dB';
     const j = c.jb;
-    $('#jb').textContent = j ? `buffer ${j.depthMs}/${j.targetMs} ms · lost ${j.lost} (fec ${j.fec}) · concealed ${j.plc} · drift-drops ${j.dropped} · underruns ${j.underruns}` : '';
+    $('#jb').textContent = j ? `buffer ${j.depthMs}/${j.targetMs} ms · lost ${j.lost} (fec ${j.fec}) · concealed ${j.plc} · late ${j.late} · drift-drops ${j.dropped} · inserted ${j.inserted} · underruns ${j.underruns}` : '';
   } else {
     setMeter($('#mIn'), 0); setMeter($('#mOut'), 0); $('#dIn').textContent = $('#dOut').textContent = ''; $('#jb').textContent = '';
   }