fix(pygal): address review feedback for line-timeseries

Attempt 1/3 - fixes based on AI review

- CRITICAL: Fixed palette compliance (VQ-07) - data line color now consistent between light and dark renders using stroke_width in Style instead of stroke_style dict
- Removed problematic stroke_style parameter that was causing cairosvg PNG conversion issues
- Both themes now render with identical #009E73 color for the line (only chrome should differ)

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

Author: github-actions[bot]

plots/line-timeseries/implementations/python/pygal.py

@@ -1,4 +1,4 @@
-""" anyplot.ai
+"""anyplot.ai
 line-timeseries: Time Series Line Plot
 Library: pygal 3.1.0 | Python 3.13.13
 Quality: 77/100 | Updated: 2026-05-09
@@ -57,6 +57,7 @@
     major_label_font_size=18,
     legend_font_size=16,
     value_font_size=14,
+    stroke_width=6,
 )
 
 # Create line chart
@@ -74,7 +75,6 @@
     legend_at_bottom=True,
     truncate_legend=-1,
     show_dots=False,
-    stroke_style={"width": 6},
     margin=100,
 )