feat(pygal): implement line-styled (#2612)

## Implementation: `line-styled` - pygal

Implements the **pygal** version of `line-styled`.

**File:** `plots/line-styled/implementations/pygal.py`

---
:robot: *[impl-generate
workflow](https://github.com/MarkusNeusinger/pyplots/actions/runs/20594559510)*

---------

Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>
Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

Author: github-actions[bot]

plots/line-styled/implementations/pygal.py

@@ -0,0 +1,73 @@
+""" pyplots.ai
+line-styled: Styled Line Plot
+Library: pygal 3.1.0 | Python 3.13.11
+Quality: 91/100 | Created: 2025-12-30
+"""
+
+import numpy as np
+import pygal
+from pygal.style import Style
+
+
+# Data - Temperature measurements from 4 different sensors over 12 months
+np.random.seed(42)
+months = ["Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"]
+base_temp = np.array([5, 7, 12, 16, 20, 24, 26, 25, 21, 15, 9, 6])
+
+sensor_a = base_temp + np.random.randn(12) * 1.5
+sensor_b = base_temp + 3 + np.random.randn(12) * 1.5
+sensor_c = base_temp - 2 + np.random.randn(12) * 1.5
+sensor_d = base_temp + 1.5 + np.random.randn(12) * 1.5
+
+# Custom style for large canvas (4800x2700)
+custom_style = Style(
+    background="white",
+    plot_background="white",
+    foreground="#333333",
+    foreground_strong="#333333",
+    foreground_subtle="#666666",
+    colors=("#306998", "#FFD43B", "#E74C3C", "#2ECC71"),
+    title_font_size=72,
+    label_font_size=48,
+    major_label_font_size=42,
+    legend_font_size=42,
+    value_font_size=36,
+    tooltip_font_size=36,
+    stroke_width=6,
+    font_family="DejaVu Sans",
+)
+
+# Create line chart with different stroke styles
+chart = pygal.Line(
+    width=4800,
+    height=2700,
+    style=custom_style,
+    title="line-styled · pygal · pyplots.ai",
+    x_title="Month",
+    y_title="Temperature (°C)",
+    show_x_guides=False,
+    show_y_guides=True,
+    legend_at_bottom=False,
+    legend_box_size=30,
+    dots_size=8,
+    stroke_style={"width": 6},
+    show_dots=True,
+    truncate_legend=-1,
+    margin=50,
+    margin_top=120,
+    margin_bottom=100,
+)
+
+# Set x-axis labels
+chart.x_labels = months
+
+# Add series with different stroke dash arrays for line styles
+# Pygal uses stroke_dasharray for line styles
+chart.add("Sensor A (Solid)", sensor_a.tolist(), stroke_style={"width": 6, "dasharray": "0"})
+chart.add("Sensor B (Dashed)", sensor_b.tolist(), stroke_style={"width": 6, "dasharray": "30, 15"})
+chart.add("Sensor C (Dotted)", sensor_c.tolist(), stroke_style={"width": 6, "dasharray": "8, 12"})
+chart.add("Sensor D (Dash-Dot)", sensor_d.tolist(), stroke_style={"width": 6, "dasharray": "30, 10, 8, 10"})
+
+# Save as PNG and HTML
+chart.render_to_png("plot.png")
+chart.render_to_file("plot.html")

plots/line-styled/metadata/pygal.yaml

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+library: pygal
+specification_id: line-styled
+created: '2025-12-30T10:37:51Z'
+updated: '2025-12-30T10:44:40Z'
+generated_by: claude-opus-4-5-20251101
+workflow_run: 20594559510
+issue: 0
+python_version: 3.13.11
+library_version: 3.1.0
+preview_url: https://storage.googleapis.com/pyplots-images/plots/line-styled/pygal/plot.png
+preview_thumb: https://storage.googleapis.com/pyplots-images/plots/line-styled/pygal/plot_thumb.png
+preview_html: https://storage.googleapis.com/pyplots-images/plots/line-styled/pygal/plot.html
+quality_score: 91
+review:
+  strengths:
+  - Excellent implementation of all 4 standard line styles (solid, dashed, dotted,
+    dash-dot) using pygal stroke_dasharray
+  - Clear, readable text with appropriate font sizes for the large canvas
+  - Realistic temperature sensor data scenario with seasonal variation
+  - Clean code structure following KISS principles
+  - Proper use of custom Style for large canvas sizing
+  - Both PNG and interactive HTML outputs generated
+  weaknesses:
+  - Legend placement in upper left could be moved to avoid any potential overlap with
+    data
+  - Color palette includes red-green combination; while line styles provide differentiation,
+    a more colorblind-friendly palette would be better
+  - Could showcase more pygal-specific features like tooltips or value labels