feat(highcharts): implement coefficient-confidence (#3601)

## Implementation: `coefficient-confidence` - highcharts

Implements the **highcharts** version of `coefficient-confidence`.

**File:** `plots/coefficient-confidence/implementations/highcharts.py`

**Parent Issue:** #3576

---
:robot: *[impl-generate
workflow](https://github.com/MarkusNeusinger/pyplots/actions/runs/20868895448)*

---------

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/coefficient-confidence/implementations/highcharts.py

@@ -0,0 +1,266 @@
+""" pyplots.ai
+coefficient-confidence: Coefficient Plot with Confidence Intervals
+Library: highcharts unknown | Python 3.13.11
+Quality: 92/100 | Created: 2026-01-09
+"""
+
+import json
+import tempfile
+import time
+import urllib.request
+from pathlib import Path
+
+import numpy as np
+from selenium import webdriver
+from selenium.webdriver.chrome.options import Options
+
+
+# Data: Coefficients from a regression model predicting housing prices
+np.random.seed(42)
+
+variables = [
+    "Square Footage",
+    "Number of Bedrooms",
+    "Number of Bathrooms",
+    "Garage Spaces",
+    "Lot Size (acres)",
+    "Year Built",
+    "Distance to City Center",
+    "School Rating",
+    "Crime Rate Index",
+    "Property Tax Rate",
+]
+
+# Generate realistic coefficients with varying significance
+coefficients = np.array([0.45, 0.12, 0.28, 0.15, 0.08, 0.02, -0.22, 0.35, -0.18, -0.05])
+std_errors = np.array([0.08, 0.09, 0.07, 0.06, 0.10, 0.04, 0.05, 0.06, 0.07, 0.08])
+
+# 95% confidence intervals
+ci_lower = coefficients - 1.96 * std_errors
+ci_upper = coefficients + 1.96 * std_errors
+
+# Determine significance (CI does not cross zero)
+significant = (ci_lower > 0) | (ci_upper < 0)
+
+# Sort by coefficient magnitude (highest at top, so reverse for display)
+sort_idx = np.argsort(coefficients)[::-1]
+variables = [variables[i] for i in sort_idx]
+coefficients = coefficients[sort_idx]
+ci_lower = ci_lower[sort_idx]
+ci_upper = ci_upper[sort_idx]
+significant = significant[sort_idx]
+
+# Download Highcharts JS
+highcharts_url = "https://code.highcharts.com/highcharts.js"
+with urllib.request.urlopen(highcharts_url, timeout=30) as response:
+    highcharts_js = response.read().decode("utf-8")
+
+highcharts_more_url = "https://code.highcharts.com/highcharts-more.js"
+with urllib.request.urlopen(highcharts_more_url, timeout=30) as response:
+    highcharts_more_js = response.read().decode("utf-8")
+
+xrange_url = "https://code.highcharts.com/modules/xrange.js"
+with urllib.request.urlopen(xrange_url, timeout=30) as response:
+    xrange_js = response.read().decode("utf-8")
+
+# Build data arrays for JavaScript
+sig_points = []
+nonsig_points = []
+
+for i, (var, coef, sig) in enumerate(zip(variables, coefficients, significant, strict=True)):
+    point = {"x": float(coef), "y": i, "name": var}
+    if sig:
+        sig_points.append(point)
+    else:
+        nonsig_points.append(point)
+
+# Convert to JS format using json for proper escaping
+categories_js = json.dumps(variables)
+sig_points_js = json.dumps(sig_points)
+nonsig_points_js = json.dumps(nonsig_points)
+
+# Build CI data for xrange series
+ci_data = []
+for i, (lower, upper, sig) in enumerate(zip(ci_lower, ci_upper, significant, strict=True)):
+    ci_data.append({"x": float(lower), "x2": float(upper), "y": i, "color": "#306998" if sig else "#B8860B"})
+
+ci_data_js = json.dumps(ci_data)
+
+# Calculate x-axis range to ensure all points are visible
+x_min = float(min(ci_lower)) - 0.05
+x_max = float(max(ci_upper)) + 0.05
+
+chart_js = f"""
+Highcharts.chart('container', {{
+    chart: {{
+        width: 4800,
+        height: 2700,
+        backgroundColor: '#ffffff',
+        marginLeft: 420,
+        marginRight: 180,
+        marginTop: 180,
+        marginBottom: 280,
+        spacingBottom: 40
+    }},
+    title: {{
+        text: 'coefficient-confidence · highcharts · pyplots.ai',
+        style: {{ fontSize: '56px', fontWeight: 'bold' }}
+    }},
+    subtitle: {{
+        text: 'Housing Price Regression Model Coefficients with 95% Confidence Intervals',
+        style: {{ fontSize: '36px', color: '#555555' }}
+    }},
+    xAxis: {{
+        min: {x_min},
+        max: {x_max},
+        title: {{
+            text: 'Coefficient Estimate (Standardized)',
+            style: {{ fontSize: '40px' }},
+            margin: 25
+        }},
+        labels: {{
+            style: {{ fontSize: '32px' }},
+            format: '{{value:.1f}}'
+        }},
+        gridLineWidth: 1,
+        gridLineColor: '#e0e0e0',
+        tickInterval: 0.1,
+        plotLines: [{{
+            value: 0,
+            color: '#666666',
+            width: 4,
+            dashStyle: 'Dash',
+            zIndex: 3,
+            label: {{
+                text: 'Null (β = 0)',
+                style: {{ fontSize: '28px', color: '#666666', fontWeight: 'bold' }},
+                rotation: 0,
+                y: 30,
+                x: 10
+            }}
+        }}]
+    }},
+    yAxis: {{
+        title: {{ text: null }},
+        categories: {categories_js},
+        labels: {{
+            style: {{ fontSize: '32px' }}
+        }},
+        gridLineWidth: 0,
+        reversed: false
+    }},
+    legend: {{
+        enabled: true,
+        itemStyle: {{ fontSize: '36px' }},
+        verticalAlign: 'bottom',
+        align: 'center',
+        layout: 'horizontal',
+        floating: false,
+        y: -20,
+        symbolRadius: 14,
+        symbolHeight: 28,
+        symbolWidth: 28,
+        itemDistance: 100
+    }},
+    tooltip: {{
+        style: {{ fontSize: '28px' }},
+        useHTML: true,
+        formatter: function() {{
+            if (this.series.type === 'xrange') {{
+                return '<b>' + this.yCategory + '</b><br/>CI: [' + this.point.x.toFixed(3) + ', ' + this.point.x2.toFixed(3) + ']';
+            }}
+            return '<b>' + this.point.name + '</b><br/>Coefficient: ' + this.x.toFixed(3);
+        }}
+    }},
+    plotOptions: {{
+        scatter: {{
+            marker: {{
+                radius: 22,
+                symbol: 'circle'
+            }},
+            zIndex: 10
+        }},
+        xrange: {{
+            borderRadius: 0,
+            pointWidth: 8,
+            zIndex: 5
+        }}
+    }},
+    series: [{{
+        type: 'xrange',
+        name: '95% CI',
+        data: {ci_data_js},
+        showInLegend: false,
+        enableMouseTracking: true
+    }}, {{
+        type: 'scatter',
+        name: 'Significant (p < 0.05)',
+        color: '#306998',
+        data: {sig_points_js},
+        marker: {{
+            fillColor: '#306998',
+            lineWidth: 0,
+            radius: 22
+        }},
+        zIndex: 10,
+        clip: false
+    }}, {{
+        type: 'scatter',
+        name: 'Not Significant',
+        color: '#FFD43B',
+        data: {nonsig_points_js},
+        marker: {{
+            fillColor: '#FFD43B',
+            lineWidth: 4,
+            lineColor: '#B8860B',
+            radius: 22
+        }},
+        zIndex: 10,
+        clip: false
+    }}]
+}});
+"""
+
+# HTML content with inline scripts
+html_content = f"""<!DOCTYPE html>
+<html>
+<head>
+    <meta charset="utf-8">
+    <script>{highcharts_js}</script>
+    <script>{highcharts_more_js}</script>
+    <script>{xrange_js}</script>
+</head>
+<body style="margin:0; padding:0; background:#ffffff;">
+    <div id="container" style="width: 4800px; height: 2700px;"></div>
+    <script>{chart_js}</script>
+</body>
+</html>"""
+
+# Write temp HTML and take screenshot
+with tempfile.NamedTemporaryFile(mode="w", suffix=".html", delete=False, encoding="utf-8") as f:
+    f.write(html_content)
+    temp_path = f.name
+
+# Save HTML for interactive version
+with open("plot.html", "w", encoding="utf-8") as f:
+    f.write(html_content)
+
+# Chrome options for headless screenshot
+chrome_options = Options()
+chrome_options.add_argument("--headless")
+chrome_options.add_argument("--no-sandbox")
+chrome_options.add_argument("--disable-dev-shm-usage")
+chrome_options.add_argument("--disable-gpu")
+chrome_options.add_argument("--window-size=4800,2800")  # Slightly larger to capture legend
+
+driver = webdriver.Chrome(options=chrome_options)
+driver.get(f"file://{temp_path}")
+time.sleep(5)  # Wait for chart to render
+
+# Get the container element and take a screenshot of just that element
+container = driver.find_element("id", "container")
+container.screenshot("plot.png")
+
+driver.quit()
+
+Path(temp_path).unlink()  # Clean up temp file