forgetest: cloud tests prove the session from the client's log and hand the head back

cloud.mode-switch took the optional connect-time firmware probe file as
the evidence of a live session and failed on a bench where that check is
off; the evidence is now gfcloud's own authenticate/ws-connect lines in
the unified log after the switch, the probe recorded when present. Cloud
mode's connect clears the kernel position counters at the head's start
and its hunt homes the head to the corner: the test tells the runner the
counters were re-zeroed (Context.counters_rezeroed) and jogs the head
back by the counter-measured displacement, and hands the lid lamp back
at the level it found. cloud.gfhome-homing documents that it leaves the
machine homed at the corner.

Baseline: a displaced head is jogged back along its own path by the
kernel-measured X/Y delta through the GRBL controller (bounded 100 mm,
waits out a controller respawn backoff); Z is never touched.

forgetest/tests/test_baseline.py

@@ -119,7 +119,8 @@ class BaselineTests(unittest.TestCase):
         self.assertEqual(set(items), {"pic/lid_led", "position"})
         self.assertEqual(items["pic/lid_led"].action, "restored")
         self.assertEqual(self._read("pic/lid_led"), "132")
-        self.assertEqual(items["position"].action, "unrestorable")
+        # no GRBL controller on the host: the head cannot be jogged back
+        self.assertTrue(items["position"].action.startswith("unrestorable"), items["position"].action)
         self.assertEqual(items["position"].found, [1000, 0, 0])
 
     def test_session_resting_lamp_from_boot_reference(self):