fix: unused variable lint error in test

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: FBumann

tests/test_figures.py

@@ -787,7 +787,7 @@ def test_bar_zero_baseline(self) -> None:
         # After overlay (which triggers _fix_animation_axis_ranges)
         combined = overlay(fig, xpx(da).line(animation_frame="frame"))
 
-        lo, hi = combined.layout.yaxis.range
+        lo, _hi = combined.layout.yaxis.range
         assert lo <= 0, f"Bar y-axis range should include 0, got lo={lo}"