test: apply timing harness review caveats

Explicit stream synchronization before/after each timed loop (refined
FixedPatchStepper stream, uniform Simulation stream, in their contexts);
required --max-wall-seconds outer timeout checked between variants and in
per-step loops; untimed finite leaf/fluid health checks; force notes for
B/C/E' (no host reads; final base interval only; whole-window average with
different summation order). Parity stays A/B/C vs A and E/E' vs E only.

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

tests/unit/test_time_refined_dfg.py

@@ -26,6 +26,14 @@ class TimingHarnessContract(unittest.TestCase):
         for name in ("A", "E"):
             self.assertTrue(t.VARIANTS[name]["force_history_valid"])
         self.assertEqual({v["case"] for v in t.VARIANTS.values()}, {"refined", "uniform"})
+        self.assertIn("final base interval", t.VARIANTS["C"]["force_note"])
+        self.assertIn("whole-window", t.VARIANTS["E'"]["force_note"])
+
+    def test_deadline(self):
+        import time
+        with self.assertRaises(TimeoutError):
+            t.check_deadline(time.monotonic() - 1)
+        t.check_deadline(time.monotonic() + 60)
 
     def test_parity_detects_bits_and_nan_masks(self):
         a = np.array([[1., np.nan], [2., 3.]], np.float32)