Add pad to theta tick labels to clear the outer circle spine

Without padding, theta labels sit right on the outer boundary.
8 points of pad applies whenever theta labels are shown — both
for full-circle plots (theta_labels=True) and partial arcs.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: iangow

plotnine/coords/coord_radial.py

@@ -248,3 +248,8 @@ def draw(self, axs: list[Axes]) -> None:
                         ax.set_rlabel_position(np.degrees(self.start) + 10)
                 else:
                     ax.set_rlabel_position(np.degrees(float(self.r_axis_inside)))
+
+            # Push theta tick labels away from the outer circle so they don't
+            # sit right on the spine.
+            if self.theta_labels or self.end is not None:
+                ax.tick_params(axis="x", pad=8)