test: retire dense-route tests, require tiles everywhere (D2)

Retired with the dense refinement route (results recorded at 1573942 and
2469af7 or named as accepted losses):
- test_refinement_blocked_base: BlockedBaseGPU exact parity (3 tests),
  DenseBlockedRouteParity (6 tests incl. MRT and two bodies),
  DenseBlockedRouteCPU (capability matrix, ledger comparator);
- test_refinement_blocked_fine: BlockedFineGPU dense-vs-blocked (3 tests);
- test_refinement_mrt_gpu: test_dense_versus_blocked_mrt_two_level;
- test_raw_exchange_gpu: test_dense_fine_storage_reference (private
  link_exchange cut-link oracle, accepted loss);
- test_refinement_gpu: test_bounded_equivalence_and_ownership (dense
  CELERIS_REFINEMENT_AUDIT ownership counters, accepted loss); its physics
  stays in test_bounded_equivalence_blocked; eight_steps loses the audit
  branch and the misleading 'ownership/counts PASS' label;
- test_fine_surface_gpu: test_fine_surface_four_hops (dense per-hop flux
  ledger, CurvedLinkSoA reflection oracle, audit counts: accepted losses;
  raw exchange covers the boundary part only, not full flux closure) and the
  dense SoA fault tests (missing surface buffer, close frees SoA); blocked
  equivalents remain in test_refinement_blocked_fine/_base;
- test_raw_exchange.test_dense_observation_rejected_before_device_access.
New TileContractCPU: level_blocks omitted/None/wrong length/None entry/
wrong arity/non-integer/bool/non-positive/non-tuple/not dividing all raise
before CUDA; whole-level tiles reach CUDA. Rejection tests and fixtures pass
tiles; launch-order and kernel-text tests follow the blocked root;
examples/fixed_periodic_patch uses whole-level tiles (+ host tile test).

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

tests/validation/multigrid/test_raw_exchange_gpu.py

@@ -92,9 +92,8 @@ def census(run, index, buffer):
 
 
 def fine(block):
-    """Two-level circle+jet construction on BOUNDS, all-blocked with a (12, 8) root tile;
-    block None is the dense route (dense reference test only, retired with the dense route)."""
-    return dict(refinements=[BOUNDS], level_blocks=[None if block is None else (12, 8), block],
+    """Two-level circle+jet construction on BOUNDS, blocked with a (12, 8) root tile."""
+    return dict(refinements=[BOUNDS], level_blocks=[(12, 8), block],
                 level_objects=[(), (circle(),)], level_jets=[(), (jet(),)])
 
 class RawExchangeGPU(unittest.TestCase):
@@ -147,26 +146,6 @@ class RawExchangeGPU(unittest.TestCase):
                         np.testing.assert_array_equal(measured.read_raw_exchange(0)['total']['impulse'],
                                                       obs['total']['impulse'])
 
-    def test_dense_fine_storage_reference(self):
-        """Same fine resolution/initial data with dense storage: a numerical
-        reference for cut-link rows, not a uniform-whole-domain convergence study."""
-        with CudaContext(0) as ctx:
-            with FixedPatchStepper(CFG, context=ctx, **fine(None)) as dense, \
-                 FixedPatchStepper(CFG, context=ctx, **fine((16, 20)), observe_raw_exchange=True) as blocked:
-                arrays = [state(l.shape) for l in blocked._levels]
-                dense.initialize(*arrays)
-                blocked.initialize(*arrays)
-                for speed in (0., .002, 0.):
-                    dense.set_jet_amplitude(0, speed)
-                    blocked.set_jet_amplitude(0, speed)
-                    dense.step(); blocked.step()
-                    for a, e in zip(blocked.download(), dense.download()):
-                        np.testing.assert_array_equal(a, e)
-                    count = dense._fine_curved.count
-                    expected = download(dense._fine_curved.link_exchange_gpu, (count, 3))
-                    actual = download(blocked._level_boundaries[1].last_raw, (count, 4))
-                    np.testing.assert_array_equal(actual[:, :3], expected)
-
     def test_depth_four_interval_storage_and_sampling(self):
         cfg = LBMConfig(nx=48, ny=48, viscosity=.02)
         obj = SimObject(0, geometry=CircleGeometry(16., 16., .5), center=(16., 16.), radius=.5)