Serial monitor redesign: Test box button, InfluxDB row in the checklist

- Test box: restart + start-up capture + online InfluxDB check (data newer
  than the restart), with a status strip; checklist and findings are the
  main view, live log / guided troubleshooting / box details are tabs,
  rarely used actions in a More menu
- light palette on all systems (macOS dark mode made the colours unreadable)
- new rule influx.invalid_value: -inf from a silent microphone makes
  InfluxDB reject every upload (HTTP 400); guide end names it
- exclusive serial port on macOS/Linux: two tool windows no longer split
  the log between them
- InfluxDB check: `since` filter, neutral wording when nothing new arrives

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

tests/test_influx.py

@@ -67,7 +67,7 @@ def test_offline_box_whose_sensors_stopped_before_status():
     latest = {"device_status": _t(29 * 60), "microphone": _t(29 * 60),
               "as7341_adc": _t(21 * 1440), "bme688": _t(21 * 1440), "sen66": _t(21 * 1440)}
     c = influx.classify(latest, NOW)
-    assert c.outcome == influx.SENSORS_MISSING and "offline now" in c.summary
+    assert c.outcome == influx.SENSORS_MISSING and "Nothing new" in c.summary
     assert any("stopped" in d for d in c.details)
     assert any("21 days ago" in d for d in c.details)
 
@@ -140,3 +140,15 @@ def test_check_device_sends_token_header_and_normalized_mac(monkeypatch):
     assert req.get_header("Authorization") == "Token tok"
     assert "tok" not in req.full_url and req.full_url.endswith("/api/v2/query?org=kota")
     assert b'"A4CB8FC9473C"' in req.data
+
+
+def test_since_ignores_data_from_before_the_test():
+    # healthy a few minutes ago, but nothing since the box was restarted by the test
+    latest = {"device_status": _t(5), "microphone": _t(5), "as7341_adc": _t(5), "bme688": _t(5), "sen66": _t(5)}
+    assert influx.classify(latest, NOW).outcome == influx.OK
+    c = influx.classify(latest, NOW, since=_t(2))
+    assert c.outcome == influx.SILENT and "since the test started" in c.summary
+    latest.update(device_status=_t(0), microphone=_t(0))
+    assert influx.classify(latest, NOW, since=_t(2)).outcome == influx.SENSORS_MISSING
+    latest.update(as7341_adc=_t(0), bme688=_t(0), sen66=_t(2.5))   # within the clock slack
+    assert influx.classify(latest, NOW, since=_t(2)).outcome == influx.OK