feat(lib): add snap_endpoints to _postprocess

tests/unit/test_postprocess.py

@@ -23,3 +23,24 @@ def test_gaussian_smooth_constant_unchanged() -> None:
     x = np.full(20, 7.5)
     result = gaussian_smooth(x, sigma=1.0)
     assert np.allclose(result, x, atol=1e-6)
+
+
+from ai_mouse._postprocess import snap_endpoints
+
+
+def test_snap_endpoints_pins_first_and_last() -> None:
+    forward = np.linspace(0.1, 0.9, 16)
+    lateral = np.full(16, 0.5)
+    f, l = snap_endpoints(forward.copy(), lateral.copy(), seq_len=16)
+    assert f[0] == 0.0
+    assert l[0] == 0.0
+    assert f[-1] == 1.0
+    assert l[-1] == 0.0
+
+
+def test_snap_endpoints_preserves_middle() -> None:
+    forward = np.linspace(0.0, 1.0, 16)
+    lateral = np.zeros(16)
+    f, _ = snap_endpoints(forward.copy(), lateral.copy(), seq_len=16, n_snap=4)
+    # Points before the last n_snap should be unchanged
+    assert np.allclose(f[1 : 16 - 4], forward[1 : 16 - 4], atol=1e-6)