docs: update documentation files and fix linting issues

tests/physics/test_exchange.py

@@ -22,7 +22,9 @@ class TestExchangePhysics:
         ex = ExchangeCorrection(Z=80)
         low_W = np.array([1.1])
         result = ex(low_W)
-        assert result[0] > 1.0, f"Exchange must enhance spectrum at low energy for heavy Z: {result[0]}"
+        assert (
+            result[0] > 1.0
+        ), f"Exchange must enhance spectrum at low energy for heavy Z: {result[0]}"
 
     @pytest.mark.physics
     def test_grows_as_energy_decreases(self):
@@ -35,7 +37,9 @@ class TestExchangePhysics:
         s_low = ex(low_W)[0]
         s_lower = ex(lower_W)[0]
 
-        assert s_lower > s_low, f"Exchange must increase at lower energy: {s_low} → {s_lower}"
+        assert (
+            s_lower > s_low
+        ), f"Exchange must increase at lower energy: {s_low} → {s_lower}"
 
     @pytest.mark.physics
     def test_vanishes_at_high_energy(self):
@@ -43,7 +47,9 @@ class TestExchangePhysics:
         ex = ExchangeCorrection(Z=40)
         high_W = np.array([3.0, 5.0])
         result = ex(high_W)
-        assert abs(result[0] - 1.0) < 0.5, f"Exchange must approach unity at high energy: {result}"
+        assert (
+            abs(result[0] - 1.0) < 0.5
+        ), f"Exchange must approach unity at high energy: {result}"
 
 
 class TestExchangeErrorHandling: