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>

examples/fixed_periodic_patch.py

@@ -48,7 +48,8 @@ def main():
                   nx=16, ny=16, viscosity=.1, velocity=1e-3, rho=1.0,
                   lattice_model="D2Q9", collision="SRT", streaming="double_buffer",
                   store_precision="FP32", ddf_shifting=False, les_enabled=False)
-    with CudaContext(0) as context, PeriodicPatchStepper(cfg, context=context, refinements=[(4, 4, 12, 12)]) as run:
+    with CudaContext(0) as context, PeriodicPatchStepper(cfg, context=context, refinements=[(4, 4, 12, 12)],
+                                                           level_blocks=[(16, 16), (24, 24)]) as run:
         p = run.patch
         coarse = shear_equilibrium(p.coarse_shape, (0, 0), 1.0, cfg.ny)
         fine = shear_equilibrium(p.fine_shape, p.fine_origin, .5, cfg.ny)