feat(plotly): implement line-stepwise (#2622)

## Implementation: `line-stepwise` - plotly

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

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

---
:robot: *[impl-generate
workflow](https://github.com/MarkusNeusinger/pyplots/actions/runs/20594557620)*

---------

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

Author: github-actions[bot]

plots/line-stepwise/implementations/plotly.py

@@ -0,0 +1,94 @@
+""" pyplots.ai
+line-stepwise: Step Line Plot
+Library: plotly 6.5.0 | Python 3.13.11
+Quality: 98/100 | Created: 2025-12-30
+"""
+
+import numpy as np
+import plotly.graph_objects as go
+
+
+# Data - Server response time monitoring (discrete state changes)
+np.random.seed(42)
+hours = np.arange(0, 24, 1)
+response_times = np.array(
+    [
+        45,
+        45,
+        42,
+        42,
+        48,
+        55,
+        65,
+        72,
+        78,
+        82,  # Morning ramp-up
+        80,
+        75,
+        85,
+        90,
+        88,
+        85,
+        78,
+        65,
+        55,
+        50,  # Afternoon peak
+        48,
+        45,
+        44,
+        43,  # Evening decline
+    ]
+)
+
+# Create step line plot
+fig = go.Figure()
+
+fig.add_trace(
+    go.Scatter(
+        x=hours,
+        y=response_times,
+        mode="lines+markers",
+        line=dict(
+            shape="hv",  # Step: horizontal then vertical
+            color="#306998",
+            width=4,
+        ),
+        marker=dict(size=14, color="#306998", line=dict(color="white", width=2)),
+        name="Response Time",
+        hovertemplate="Hour: %{x}<br>Response: %{y} ms<extra></extra>",
+    )
+)
+
+# Layout
+fig.update_layout(
+    title=dict(text="line-stepwise · plotly · pyplots.ai", font=dict(size=28), x=0.5, xanchor="center"),
+    xaxis=dict(
+        title=dict(text="Hour of Day", font=dict(size=22)),
+        tickfont=dict(size=18),
+        tickmode="linear",
+        tick0=0,
+        dtick=2,
+        range=[-0.5, 23.5],
+        showgrid=True,
+        gridcolor="rgba(128, 128, 128, 0.2)",
+        gridwidth=1,
+    ),
+    yaxis=dict(
+        title=dict(text="Response Time (ms)", font=dict(size=22)),
+        tickfont=dict(size=18),
+        range=[35, 95],
+        showgrid=True,
+        gridcolor="rgba(128, 128, 128, 0.2)",
+        gridwidth=1,
+    ),
+    template="plotly_white",
+    showlegend=False,
+    margin=dict(l=100, r=80, t=120, b=100),
+    plot_bgcolor="white",
+)
+
+# Save as PNG (4800 x 2700 px)
+fig.write_image("plot.png", width=1600, height=900, scale=3)
+
+# Save as HTML for interactivity
+fig.write_html("plot.html", include_plotlyjs="cdn")

plots/line-stepwise/metadata/plotly.yaml

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+library: plotly
+specification_id: line-stepwise
+created: '2025-12-30T10:38:26Z'
+updated: '2025-12-30T10:46:33Z'
+generated_by: claude-opus-4-5-20251101
+workflow_run: 20594557620
+issue: 0
+python_version: 3.13.11
+library_version: 6.5.0
+preview_url: https://storage.googleapis.com/pyplots-images/plots/line-stepwise/plotly/plot.png
+preview_thumb: https://storage.googleapis.com/pyplots-images/plots/line-stepwise/plotly/plot_thumb.png
+preview_html: https://storage.googleapis.com/pyplots-images/plots/line-stepwise/plotly/plot.html
+quality_score: 98
+review:
+  strengths:
+  - Perfect implementation of step function using Plotly shape=hv parameter
+  - Excellent realistic data scenario (server response time monitoring over 24 hours)
+  - Clean code following KISS principles with proper font sizes for 4800x2700 output
+  - Interactive HTML output with custom hover template showing hour and response time
+  - Well-balanced layout with good canvas utilization
+  weaknesses:
+  - 'Minor: Grid/legend criterion loses 2 points due to disabled legend, though acceptable
+    for single-series plots'