feat(plotly): implement line-annotated-events (#3032)

## Implementation: `line-annotated-events` - plotly

Implements the **plotly** version of `line-annotated-events`.

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

**Parent Issue:** #2997

---
:robot: *[impl-generate
workflow](https://github.com/MarkusNeusinger/pyplots/actions/runs/20617489094)*

---------

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

Author: github-actions[bot]

plots/line-annotated-events/implementations/plotly.py

@@ -0,0 +1,128 @@
+""" pyplots.ai
+line-annotated-events: Annotated Line Plot with Event Markers
+Library: plotly 6.5.0 | Python 3.13.11
+Quality: 92/100 | Created: 2025-12-31
+"""
+
+import numpy as np
+import pandas as pd
+import plotly.graph_objects as go
+
+
+# Data - Simulated stock price data with events
+np.random.seed(42)
+
+# Generate daily stock prices over a year
+dates = pd.date_range("2024-01-01", periods=252, freq="B")  # Business days
+returns = np.random.normal(0.0005, 0.015, len(dates))
+prices = 100 * np.exp(np.cumsum(returns))
+
+# Define significant events (earnings announcements, product launches)
+events = [
+    {"date": pd.Timestamp("2024-01-25"), "label": "Q4 Earnings"},
+    {"date": pd.Timestamp("2024-03-15"), "label": "Product Launch"},
+    {"date": pd.Timestamp("2024-04-24"), "label": "Q1 Earnings"},
+    {"date": pd.Timestamp("2024-06-10"), "label": "Expansion Announced"},
+    {"date": pd.Timestamp("2024-07-25"), "label": "Q2 Earnings"},
+    {"date": pd.Timestamp("2024-09-20"), "label": "Partnership Deal"},
+    {"date": pd.Timestamp("2024-10-24"), "label": "Q3 Earnings"},
+]
+
+# Create figure
+fig = go.Figure()
+
+# Add main price line
+fig.add_trace(
+    go.Scatter(
+        x=dates,
+        y=prices,
+        mode="lines",
+        name="Stock Price",
+        line={"color": "#306998", "width": 4},
+        hovertemplate="Date: %{x|%Y-%m-%d}<br>Price: $%{y:.2f}<extra></extra>",
+    )
+)
+
+# Add vertical lines and markers for events with alternating heights
+y_range = prices.max() - prices.min()
+heights = [0.92, 0.82, 0.92, 0.82, 0.92, 0.82, 0.92]  # Alternating heights
+
+for i, event in enumerate(events):
+    event_date = event["date"]
+    event_label = event["label"]
+    y_position = prices.min() + y_range * heights[i]
+
+    # Find the closest price at event date
+    closest_idx = np.abs(dates - event_date).argmin()
+    price_at_event = prices[closest_idx]
+
+    # Add vertical dashed line
+    fig.add_shape(
+        type="line",
+        x0=event_date,
+        x1=event_date,
+        y0=prices.min() - y_range * 0.02,
+        y1=y_position - y_range * 0.02,
+        line={"color": "#FFD43B", "width": 3, "dash": "dash"},
+    )
+
+    # Add marker at the event date on the price line
+    fig.add_trace(
+        go.Scatter(
+            x=[event_date],
+            y=[price_at_event],
+            mode="markers",
+            marker={"size": 18, "color": "#FFD43B", "symbol": "diamond", "line": {"color": "#306998", "width": 2}},
+            showlegend=False,
+            hovertemplate=f"{event_label}<br>Date: %{{x|%Y-%m-%d}}<br>Price: $%{{y:.2f}}<extra></extra>",
+        )
+    )
+
+    # Add annotation label
+    fig.add_annotation(
+        x=event_date,
+        y=y_position,
+        text=event_label,
+        showarrow=False,
+        font={"size": 20, "color": "#333333"},
+        bgcolor="rgba(255, 212, 59, 0.9)",
+        bordercolor="#FFD43B",
+        borderwidth=2,
+        borderpad=8,
+    )
+
+# Update layout
+fig.update_layout(
+    title={"text": "line-annotated-events · plotly · pyplots.ai", "font": {"size": 40}, "x": 0.5, "xanchor": "center"},
+    xaxis={
+        "title": {"text": "Date", "font": {"size": 36}},
+        "tickfont": {"size": 28},
+        "showgrid": True,
+        "gridcolor": "rgba(0,0,0,0.1)",
+        "gridwidth": 1,
+    },
+    yaxis={
+        "title": {"text": "Stock Price (USD)", "font": {"size": 36}},
+        "tickfont": {"size": 28},
+        "tickprefix": "$",
+        "showgrid": True,
+        "gridcolor": "rgba(0,0,0,0.1)",
+        "gridwidth": 1,
+    },
+    template="plotly_white",
+    showlegend=True,
+    legend={
+        "x": 0.02,
+        "y": 0.98,
+        "font": {"size": 24},
+        "bgcolor": "rgba(255,255,255,0.9)",
+        "bordercolor": "rgba(0,0,0,0.2)",
+        "borderwidth": 1,
+    },
+    margin={"l": 120, "r": 50, "t": 120, "b": 100},
+    plot_bgcolor="white",
+)
+
+# Save as PNG and HTML
+fig.write_image("plot.png", width=1600, height=900, scale=3)
+fig.write_html("plot.html", include_plotlyjs=True)

plots/line-annotated-events/metadata/plotly.yaml

@@ -0,0 +1,25 @@
+library: plotly
+specification_id: line-annotated-events
+created: '2025-12-31T10:56:37Z'
+updated: '2025-12-31T11:08:03Z'
+generated_by: claude-opus-4-5-20251101
+workflow_run: 20617489094
+issue: 2997
+python_version: 3.13.11
+library_version: 6.5.0
+preview_url: https://storage.googleapis.com/pyplots-images/plots/line-annotated-events/plotly/plot.png
+preview_thumb: https://storage.googleapis.com/pyplots-images/plots/line-annotated-events/plotly/plot_thumb.png
+preview_html: https://storage.googleapis.com/pyplots-images/plots/line-annotated-events/plotly/plot.html
+quality_score: 92
+review:
+  strengths:
+  - Excellent use of alternating annotation heights to prevent label overlap
+  - High-quality visual design with appropriate font sizes for 4800x2700 canvas
+  - Clean color scheme with good contrast (blue line, yellow annotations)
+  - Interactive hover templates provide rich information
+  - Realistic stock price scenario with appropriate event types
+  - Proper use of Plotly shape and annotation features
+  weaknesses:
+  - Grid lines are very subtle (alpha 0.1) - could be slightly more visible at 0.2-0.3
+  - Does not leverage Plotly-specific interactive features like rangeslider
+  - Creates both PNG and HTML outputs when only PNG is required