The critical tier proven on a rising loop; the board temperatures watched

forgectrl pin 76115fd: the chassis LM75 and the supply sensor ride /status
as temps (degrees and a raw count), the engine ranges them over every run
session into one run-end line, and a critical fault that clears with its
session yields the reason to the standing hold.

Bench: critical_tier_drill.py (a bench tool now, registered as
critical-tier) sets the ceiling, the resume gate and the critical line a
few tenths above the live upstream reading and lets the engine's own
flow-check heater warm the loop through them inside one M8 session;
temp_calibrate.py gains supply-watch, supply-point and supply-fit for the
supply sensor against a thermometer on its heatsink, the fit shown beside
UAPI.md's unverified guess.

Catalog: cooling.gate-off checks the /status temps fields and the run-end
board-temperature line (the unit fake mirrors both, one new failure
case); cooling.critical-tier checks the reason after a faulted session.

Docs: CAMPAIGN-LOG entries for cooling.critical-tier on dev image
20260822154257 and the warm-loop drill (OVERTEMP at 10 s, CRITICAL at
14 s, the fault ending with the session); BRINGUP item 19, the facts bank
(board temperatures at idle), COOLING section 9, the bench README.

forgetest/tests/test_cooling_suite.py

@@ -229,11 +229,13 @@ class GateOffTests(unittest.TestCase):
         cooling.SESSION_END_WAIT_S = 3
         self.fc.state["status"] = dict(self.fc.state["status"],
                                        coolant={"down_c": 22.4, "up_c": 22.3, "pump": True, "tec": False},
+                                       temps={"chassis_c": 29.0, "supply_raw": 589},
                                        gates_off=[])
         self.fc.state["cool"] = {"phase": "idle", "verdict": "OK", "fire_ok": False, "hold": False,
                                  "gates_off": []}
         self.fc.state["settings"].update({"cool_temp_max": "", "cool_temp_resume": ""})
         self.log_line = True        # the engine writes its run-start line
+        self.temps_line = True      # the engine writes its run-end temperature line
         self.report_off = True      # the engine reports the off gate
         self.trips = True           # the engine trips a low ceiling
         self.sessions = 0           # run sessions the engine saw (M8 with the phase not run)
@@ -279,6 +281,10 @@ class GateOffTests(unittest.TestCase):
             def end():
                 time.sleep(0.3)
                 cool["phase"] = "smoke"
+                if self.temps_line:
+                    self.fc.state["logs_tail"]["text"] += (
+                        "Aug 22 12:00:30 forgectrl: cool: temps this job: chassis 29.0..29.4 C, "
+                        "supply raw 587..592\n")
                 time.sleep(0.2)
                 cool["phase"] = "idle"
             threading.Thread(target=end, daemon=True).start()
@@ -367,6 +373,12 @@ class GateOffTests(unittest.TestCase):
         self.assertIn("run-start log line", str(cm.exception))
         self.assertEqual(self.fc.state["settings"]["cool_temp_max"], "")
 
+    def test_a_missing_run_end_temperature_line_fails(self):
+        self.temps_line = False
+        with self.assertRaises(Failed) as cm:
+            self.run_test()
+        self.assertIn("board-temperature line", str(cm.exception))
+
     def test_a_custom_ceiling_is_restored_verbatim(self):
         self.fc.state["settings"].update({"cool_temp_max": "30", "cool_temp_resume": "28"})
         self._describe()