Power-off spike (Part A) on the N100: plugswitch, wall-power figures, the hub's view

plugswitch.py refuses 'off' unless 20 s of readings show the N100 is already off (standby + 1 W,
no ping); 7 tests, each check red-proofed. By hand: guest shutdown 12 s, host off, 0.0 W; the hub
stayed silent and 'ONLINE' for 18 min; plug off/on did not start the N100, its power button did
(dashboard in 42 s). Wall figures into SIZING.md 4 and sizing.json power (8.5 / 20.7 / 0.0 W).

scripts/bench/test_plugswitch.py

@@ -0,0 +1,40 @@
+#!/usr/bin/env python3
+"""Pins plugswitch.py's rule: `off` only when 20 s of readings show the machine is off."""
+import os, sys, unittest
+sys.path.insert(0, os.path.dirname(os.path.abspath(__file__)))
+from plugswitch import off_allowed  # noqa: E402
+
+OFF = [(t, 0.4, False) for t in range(0, 20, 2)]
+
+
+class Rule(unittest.TestCase):
+    def test_off_machine_allowed(self):
+        self.assertTrue(off_allowed(OFF, 0.3)[0])
+
+    def test_running_machine_refused_by_watts(self):
+        s = OFF[:5] + [(10, 7.2, False)] + OFF[6:]
+        ok, why = off_allowed(s, 0.3)
+        self.assertFalse(ok); self.assertIn('draws power', why)
+
+    def test_ping_answer_refused(self):
+        s = OFF[:-1] + [(18, 0.4, True)]
+        ok, why = off_allowed(s, 0.3)
+        self.assertFalse(ok); self.assertIn('ping', why)
+
+    def test_failed_read_refused(self):
+        s = OFF[:3] + [(6, None, False)] + OFF[4:]
+        self.assertFalse(off_allowed(s, 0.3)[0])
+
+    def test_short_window_refused(self):
+        self.assertFalse(off_allowed(OFF[:4], 0.3)[0])
+
+    def test_no_standby_refused(self):
+        self.assertFalse(off_allowed(OFF, None)[0])
+
+    def test_edge_exactly_at_limit_refused(self):
+        s = OFF[:-1] + [(18, 1.3, False)]
+        self.assertFalse(off_allowed(s, 0.3)[0])
+
+
+if __name__ == '__main__':
+    unittest.main()