Gate OSWEC refinement against published motion

PARITY.md

@@ -870,8 +870,12 @@ separate from Python's default implicit added mass.
 
 A [four-step R2025b refinement](https://github.com/cmudrc/wec-sim-python/actions/runs/38093454463)
 keeps the published 120 s, 2.5 m/8 s regular wave, 40 s ramp, hinge, and mesh
-hydrodynamics. Disabling pressure and VTP output changes the original 0.1 s
-pitch trace by exactly zero. Halving the MATLAB `ode4` and nonlinear-force
+hydrodynamics. Disabling pressure and VTP output leaves all 1,201 samples of
+the original 0.1 s flap pose, velocity, acceleration, excitation, radiation,
+added-mass, and restoring-force histories exactly unchanged. The refined-step
+gate now compares its coarse run against a compact
+[published-case source fixture](tests/fixtures/matlab/README.md) before
+testing Python motion. Halving the MATLAB `ode4` and nonlinear-force
 sample steps from `0.1` to `0.05`, `0.05` to `0.025`, and `0.025` to
 `0.0125` s changes pitch by at most `0.005581`, `0.001295`, and
 `0.000317` rad, respectively. The public `WEC.fixed_hinge` path now

tests/fixtures/matlab/README.md

@@ -1,5 +1,23 @@
 # Portable MATLAB reference data
 
+## OSWEC nonlinear visualization motion
+
+`oswec_nonlinear_viz_published_motion.npz` keeps all 1,201 samples of the
+published 120 s, 0.1 s `ode4` flap motion and its principal force channels.
+It was copied without rounding from the untouched R2025b
+[published-case run](https://github.com/cmudrc/wec-sim-python/actions/runs/38259283403)
+(`matlab-oswec-nonlinear-viz-pressure` artifact, run commit
+`1083a1f29725785cbba0cb67f8e389a9cade16fc`). The workflow pins WEC-Sim
+core `0753b2e47f2457c078751dcfe5d251d1767b80ab` and Applications
+`d53d4d4c9eda2581f04204f5d394a6ef84bb099e`. The source `source.mat`
+hash is `f5c2944777f35741a48034e64fb4d3d7ec165466f6f2fc76f7be1f38383ad466`.
+The archive contains `time`, `pose`, `velocity`, `acceleration`,
+`forceExcitation`, `forceRadiationDamping`, `forceAddedMass`, and
+`forceRestoring` for the six flap degrees of freedom. Its SHA-256 is
+`63f3669b192ab271a92f5ea9c4650d1d183ef68f0abc4a6b0faedcd2b4948e4f`.
+The refined-step source job gates its 0.1 s run against these published
+channels before evaluating step sensitivity or independent Python motion.
+
 ## RM3 regular wave
 
 `rm3_regular_wave.npz` contains selected motion and PTO channels at every

tests/test_oswec_nonlinear_viz_motion.py

@@ -29,6 +29,17 @@ def test_published_nonlinear_oswec_hinge_against_refined_matlab():
         assert float(source["nonlinearDt"].item()) == dt
         assert str(source["solver"].item()) == "ode4"
         assert len(source["time"].ravel()) == round(120 / dt) + 1
+    # The refinement disables pressure and ParaView output. Its coarse run
+    # must still reproduce the untouched published case before comparisons
+    # with finer source steps can be interpreted as step sensitivity.
+    fixture = (Path(__file__).parent / "fixtures" / "matlab"
+               / "oswec_nonlinear_viz_published_motion.npz")
+    with np.load(fixture) as published:
+        np.testing.assert_array_equal(coarse["time"].ravel(), published["time"])
+        for channel in ("pose", "velocity", "acceleration",
+                        "forceExcitation", "forceRadiationDamping",
+                        "forceAddedMass", "forceRestoring"):
+            np.testing.assert_array_equal(coarse[channel], published[channel])
     np.testing.assert_allclose(coarse["time"].ravel(),
                                medium["time"].ravel()[::2], rtol=0, atol=1e-12)
     np.testing.assert_allclose(medium["time"].ravel(),