feat(seaborn): implement line-stepwise (#2848)

## Implementation: `line-stepwise` - seaborn

Implements the **seaborn** version of `line-stepwise`.

**File:** `plots/line-stepwise/implementations/seaborn.py`

---
:robot: *[impl-generate
workflow](https://github.com/MarkusNeusinger/pyplots/actions/runs/20606633234)*

---------

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Author: github-actions[bot]

plots/line-stepwise/implementations/seaborn.py

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+""" pyplots.ai
+line-stepwise: Step Line Plot
+Library: seaborn 0.13.2 | Python 3.13.11
+Quality: 92/100 | Created: 2025-12-30
+"""
+
+import matplotlib.pyplot as plt
+import numpy as np
+import seaborn as sns
+
+
+# Data - Daily server load showing discrete state changes
+np.random.seed(42)
+hours = np.arange(0, 24)
+# Simulate server load with discrete jumps at certain hours
+base_load = np.array([20, 20, 15, 15, 15, 25, 40, 65, 80, 85, 85, 75, 70, 75, 80, 85, 90, 85, 70, 55, 45, 35, 30, 25])
+load_noise = np.random.randint(-3, 4, size=24)
+server_load = np.clip(base_load + load_noise, 10, 100)
+
+# Create figure
+fig, ax = plt.subplots(figsize=(16, 9))
+sns.set_style("whitegrid")
+
+# Step line plot using seaborn lineplot with drawstyle
+# seaborn's lineplot wraps matplotlib, so we use drawstyle for step effect
+sns.lineplot(x=hours, y=server_load, ax=ax, drawstyle="steps-post", linewidth=3, color="#306998")
+
+# Add markers at each data point for clarity
+sns.scatterplot(x=hours, y=server_load, ax=ax, s=150, color="#FFD43B", edgecolor="#306998", linewidth=2, zorder=5)
+
+# Styling
+ax.set_xlabel("Hour of Day", fontsize=20)
+ax.set_ylabel("Server Load (%)", fontsize=20)
+ax.set_title("line-stepwise · seaborn · pyplots.ai", fontsize=24)
+ax.tick_params(axis="both", labelsize=16)
+
+# Set axis limits
+ax.set_xlim(-0.5, 23.5)
+ax.set_ylim(0, 105)
+
+# Customize grid
+ax.grid(True, alpha=0.3, linestyle="--")
+
+# Set x-ticks to show every 2 hours
+ax.set_xticks(np.arange(0, 24, 2))
+
+plt.tight_layout()
+plt.savefig("plot.png", dpi=300, bbox_inches="tight")

plots/line-stepwise/metadata/seaborn.yaml

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+library: seaborn
+specification_id: line-stepwise
+created: '2025-12-30T21:51:58Z'
+updated: '2025-12-30T21:54:12Z'
+generated_by: claude-opus-4-5-20251101
+workflow_run: 20606633234
+issue: 0
+python_version: 3.13.11
+library_version: 0.13.2
+preview_url: https://storage.googleapis.com/pyplots-images/plots/line-stepwise/seaborn/plot.png
+preview_thumb: https://storage.googleapis.com/pyplots-images/plots/line-stepwise/seaborn/plot_thumb.png
+preview_html: null
+quality_score: 92
+review:
+  strengths:
+  - Excellent visualization of step function with clear horizontal and vertical transitions
+  - Realistic server load scenario that demonstrates the plot type well
+  - Perfect text sizing and legibility at target resolution
+  - Good use of markers to highlight actual data points on the step line
+  - Clean color scheme (Python blue/yellow) with good colorblind accessibility
+  - Proper title format following spec-id · library · pyplots.ai convention
+  weaknesses:
+  - sns.set_style("whitegrid") is called after figure creation, which may not apply
+    the style correctly (should be called before plt.subplots)
+  - Limited use of seaborn-specific features - the implementation relies heavily on
+    matplotlib drawstyle parameter passed through seaborn