feat(analysis): add 2D political compass and 2D trajectories

- compute_2d_axes (PCA + anchor)
- compute_2d_trajectories
- plot_political_compass, plot_2d_trajectories
- unit test: tests/test_political_compass.py

tests/test_political_compass.py

@@ -0,0 +1,44 @@
+import numpy as np
+import types
+import sys
+
+import pytest
+
+
+def test_compute_2d_axes_pca_synthetic(monkeypatch):
+    """Synthetic test for compute_2d_axes using patched alignment helper."""
+
+    # Create a fake trajectory module with required helpers
+    fake_traj = types.SimpleNamespace()
+
+    # _load_window_ids should return ordered windows
+    fake_traj._load_window_ids = lambda db: ["w1", "w2"]
+
+    # _load_mp_vectors_for_window is not used because we patch _procrustes_align_windows
+    fake_traj._load_mp_vectors_for_window = lambda db, w: {}
+
+    # Provide aligned vectors directly
+    aligned = {
+        "w1": {"Alice": np.array([1.0, 0.0, 0.0]), "Bob": np.array([0.0, 1.0, 0.0])},
+        "w2": {"Alice": np.array([0.8, 0.2, 0.0]), "Bob": np.array([0.1, 0.9, 0.0])},
+    }
+
+    fake_traj._procrustes_align_windows = lambda x: aligned
+
+    # Insert fake module into sys.modules for import by analysis.political_axis
+    monkeypatch.setitem(sys.modules, "analysis.trajectory", fake_traj)
+
+    # Now import the function under test
+    from analysis.political_axis import compute_2d_axes
+
+    positions_by_window, axis_def = compute_2d_axes(
+        db_path="dummy", window_ids=["w1", "w2"], method="pca"
+    )
+
+    assert "w1" in positions_by_window and "w2" in positions_by_window
+    for wid in ("w1", "w2"):
+        for name, coord in positions_by_window[wid].items():
+            assert len(coord) == 2
+            assert np.isfinite(coord[0]) and np.isfinite(coord[1])
+
+    assert axis_def.get("method") == "pca"