Keep RM3 stop transition source samples in portable CI

tests/fixtures/matlab/README.md

@@ -54,6 +54,22 @@ That HDF5 is not byte-identical to the current WEC-Sim example; its regular-wave
 hydrodynamic data still reproduce this source trajectory within the stated
 per-channel gates. The live paired tests continue to use pinned MATLAB inputs.
 
+## RM3 end-stop force transition
+
+`rm3_end_stops_force_samples.csv` retains six rows from the successful
+[full-duration 0.0125 s R2025b run](https://github.com/cmudrc/wec-sim-python/actions/runs/37698235851)
+(`matlab-RM3_END_STOPS_FULL_FINER-baseline` artifact, run commit
+`ae9a0a8e0959b95a9489b61ea9c6f161ae184e7e`). The workflow pins core
+`0753b2e47f2457c078751dcfe5d251d1767b80ab` and Applications
+`d53d4d4c9eda2581f04204f5d394a6ef84bb099e`. Source rows
+`0, 5166, 8627, 8948, 22725, 28451` retain CSV columns `0, 3, 9, 15`
+as time, stroke, speed, and total PTO force. The source CSV SHA-256 is
+`898147eeac1bc62746dfb84a71dec9d640bbcafb9da63129ef9040467398f7d0`;
+the compact fixture SHA-256 is
+`a409f621d21825366dc1f11b13c12fc9c88f07beb6f86a4670a709253c7f3c20`.
+Two selected rows are inside the effective 0.1 mm spring transition and
+distinguish the source's smooth force from a sharp stop.
+
 ## Sphere free decay
 
 `sphere_free_decay.npz` retains every sample of the five published Sphere

tests/fixtures/matlab/rm3_end_stops_force_samples.csv

@@ -0,0 +1,7 @@
+source_row,time_s,stroke_m,speed_m_per_s,total_force_n
+0,0,0,0,-4.8784927946264703e-25
+5166,64.575000000000003,0.59986018228918703,-0.00120895311809712,1450.7437417165499
+8627,107.83750000000001,-0.66401256505767803,0.0096621411218380908,6389661.9364213701
+8948,111.84999999999999,0.66414522911501095,0.012065261787550199,-6429001.2256459901
+22725,284.0625,-0.600025582654659,0.41576599328819702,-498502.564619813
+28451,355.63749999999999,-0.60007629978782195,-0.49465971604444098,600139.05699970899

tests/test_rm3_end_stops_standalone.py

@@ -13,6 +13,29 @@
 ROOT = Path(__file__).resolve().parents[1]
 EXAMPLE = ROOT / "examples/rm3.json"
 HYDRO = ROOT / "examples/data/rm3.h5"
+SOURCE_FORCE = (ROOT / "tests/fixtures/matlab"
+                / "rm3_end_stops_force_samples.csv")
+
+
+def test_published_stop_transition_matches_compact_matlab_source():
+    samples = np.loadtxt(SOURCE_FORCE, delimiter=",", skiprows=1)
+    assert samples.shape == (6, 5)
+    np.testing.assert_array_equal(samples[:, 0],
+                                  [0, 5166, 8627, 8948, 22725, 28451])
+    stroke, speed, source_force = samples[:, 2], samples[:, 3], samples[:, 4]
+    stops = LinearHardStops(-0.6, 0.6, 1e8, 1e8)
+    predicted = -1_200_000 * speed + stops.force(stroke, speed)
+    np.testing.assert_allclose(predicted, source_force, rtol=0, atol=1e-5)
+
+    # Two source samples lie inside the 0.1 mm transition. A sharp spring
+    # misses each logged total PTO force by more than 1 kN there.
+    transition = (np.abs(stroke) > 0.6) & (np.abs(stroke) < 0.6001)
+    assert np.count_nonzero(transition) == 2
+    sharp_force = (-1_200_000 * speed
+                   + 1e8 * np.maximum(-0.6 - stroke, 0)
+                   - 1e8 * np.maximum(stroke - 0.6, 0))
+    assert np.min(np.abs(sharp_force[transition]
+                         - source_force[transition])) > 1000
 
 
 def test_opt_in_stops_are_step_stable_and_report_the_reaction():