feat(lib): add resample_arc, build_timestamps

tests/unit/test_postprocess.py

@@ -72,3 +72,35 @@ def test_enforce_forward_monotonic_clips_to_unit_interval() -> None:
     out = enforce_forward_monotonic(f.copy())
     assert out[0] == 0.0
     assert out[-1] == 1.0
+
+
+from ai_mouse._postprocess import build_timestamps, resample_arc
+
+
+def test_resample_arc_identity_when_same_length() -> None:
+    pts = np.array([[0.0, 0.0], [1.0, 1.0], [2.0, 0.0], [3.0, 1.0]])
+    out = resample_arc(pts, 4)
+    assert np.allclose(out, pts, atol=1e-6)
+
+
+def test_resample_arc_changes_length() -> None:
+    pts = np.array([[float(i), 0.0] for i in range(10)])
+    out = resample_arc(pts, 5)
+    assert out.shape == (5, 2)
+    # Endpoints preserved
+    assert np.allclose(out[0], pts[0])
+    assert np.allclose(out[-1], pts[-1])
+
+
+def test_build_timestamps_strictly_increasing() -> None:
+    log_dt = np.array([0.0, 2.0, 2.5, 3.0, 2.0])
+    ts = build_timestamps(log_dt, total_duration_ms=200.0)
+    assert ts[0] == 0
+    assert np.all(np.diff(ts) >= 1)  # at least 1 ms apart
+
+
+def test_build_timestamps_total_close_to_target() -> None:
+    log_dt = np.array([1.0] * 10)
+    ts = build_timestamps(log_dt, total_duration_ms=300.0)
+    # Last timestamp should be roughly total - one slot
+    assert abs(ts[-1] - 270) < 60  # tolerant of clipping