Flow-detection experimental record and bench tooling

Adds the design matrix and its supporting tools, and records in BRINGUP
what the 60-run matrix overturned: sub-40-percent duty mimics flow
(three of five dead-pump trials looked healthier than a working pump),
the operating point and threshold now rest on 25 pooled observations,
periodic re-checks are thermally free with the fans running, and the
settle gate closes a bench-proven miss. Also records what is NOT yet
validated - warm-loop baselines and behaviour under laser heating - as
first-light commissioning items.

scripts/bench/temp_calibration.json

@@ -0,0 +1,11 @@
+{
+  "points": [
+    {
+      "measured_c": 25.67,
+      "raw1": 672.4,
+      "raw2": 672.6,
+      "note": "IR on reservoir+hoses 78.2F, ambient 78.0F, idle 1h, pump on, heater off",
+      "when": "2026-08-02 18:13:41"
+    }
+  ]
+}