update(arc-basic): highcharts — new implementation (#4374)

## Summary

New **highcharts** implementation for **arc-basic**.

### Changes
- Created new highcharts implementation from scratch
- Uses Highcharts arc diagram series type

## Test Plan
- [x] Preview images uploaded to GCS staging
- [x] Implementation file passes ruff format/check
- [x] Metadata YAML created with current versions
- [ ] Automated review triggered

---
Generated with [Claude Code](https://claude.com/claude-code) `/update`
command

---------

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: MarkusNeusinger

plots/arc-basic/implementations/highcharts.py

@@ -0,0 +1,237 @@
+""" pyplots.ai
+arc-basic: Basic Arc Diagram
+Library: highcharts 1.10.3 | Python 3.14.3
+Quality: 87/100 | Created: 2026-02-23
+"""
+
+import json
+import tempfile
+import time
+import urllib.request
+from pathlib import Path
+
+from PIL import Image
+from selenium import webdriver
+from selenium.webdriver.chrome.options import Options
+
+
+# Data: Character interactions in a story chapter
+nodes = ["Alice", "Bob", "Carol", "David", "Eve", "Frank", "Grace", "Henry", "Iris", "Jack"]
+
+# Edges: (source, target, weight) — dialogue exchange count
+edges = [
+    ("Alice", "Bob", 5),
+    ("Alice", "David", 3),
+    ("Bob", "Carol", 3),
+    ("Carol", "Eve", 2),
+    ("David", "Frank", 3),
+    ("Eve", "Grace", 1),
+    ("Alice", "Henry", 2),
+    ("Bob", "Frank", 3),
+    ("Carol", "David", 4),
+    ("Frank", "Iris", 1),
+    ("Grace", "Jack", 2),
+    ("Alice", "Jack", 1),
+    ("David", "Henry", 3),
+    ("Henry", "Iris", 2),
+    ("Iris", "Jack", 3),
+]
+
+# Node connection counts for marker sizing
+degree = dict.fromkeys(nodes, 0)
+for src, tgt, _ in edges:
+    degree[src] += 1
+    degree[tgt] += 1
+
+# Colorblind-safe palette — Python Blue anchor with complementary tones
+node_colors = {
+    "Alice": "#306998",
+    "Bob": "#E8A317",
+    "Carol": "#17BECF",
+    "David": "#9467BD",
+    "Eve": "#2CA02C",
+    "Frank": "#D4652F",
+    "Grace": "#8C564B",
+    "Henry": "#1F77B4",
+    "Iris": "#E377C2",
+    "Jack": "#5DA88A",
+}
+
+# Node config with degree-scaled markers (3-4x default for 4800x2700)
+nodes_data = []
+for name in nodes:
+    nodes_data.append(
+        {
+            "id": name,
+            "color": node_colors[name],
+            "marker": {"radius": 95 + degree[name] * 14, "lineWidth": 5, "lineColor": "#ffffff"},
+        }
+    )
+
+# Scale weights up for visual node sizing (arc diagram sizes nodes by total weight flow)
+weight_scale = 14
+links_data = [{"from": src, "to": tgt, "weight": w * weight_scale} for src, tgt, w in edges]
+
+# Chart options (raw JS — highcharts_core doesn't support arcdiagram type)
+chart_options = {
+    "chart": {
+        "width": 4800,
+        "height": 2700,
+        "backgroundColor": "#ffffff",
+        "marginTop": 150,
+        "marginBottom": 10,
+        "marginLeft": 200,
+        "marginRight": 200,
+        "spacingTop": 20,
+        "spacingBottom": 0,
+    },
+    "title": {
+        "text": "arc-basic \u00b7 highcharts \u00b7 pyplots.ai",
+        "style": {"fontSize": "56px", "fontWeight": "bold", "color": "#333333"},
+        "margin": 30,
+    },
+    "subtitle": {
+        "text": "Character interactions — Dialogue exchanges between characters in a story chapter",
+        "style": {"fontSize": "36px", "color": "#666666"},
+    },
+    "accessibility": {"enabled": False},
+    "tooltip": {
+        "style": {"fontSize": "32px"},
+        "nodeFormat": "{point.name}: {point.sum} exchanges",
+        "pointFormat": "{point.fromNode.name} \u2192 {point.toNode.name}: {point.weight} exchanges",
+    },
+    "series": [
+        {
+            "type": "arcdiagram",
+            "name": "Interactions",
+            "keys": ["from", "to", "weight"],
+            "nodes": nodes_data,
+            "data": links_data,
+            "colorByPoint": True,
+            "centeredLinks": True,
+            "linkColorMode": "from",
+            "linkOpacity": 0.5,
+            "linkWeight": 18,
+            "equalNodes": False,
+            "nodeWidth": 110,
+            "minLinkWidth": 8,
+            "marker": {"radius": 110, "lineWidth": 5, "lineColor": "#ffffff"},
+            "dataLabels": [
+                {
+                    "enabled": True,
+                    "rotation": 0,
+                    "y": 80,
+                    "align": "center",
+                    "style": {
+                        "fontSize": "48px",
+                        "fontWeight": "bold",
+                        "textOutline": "3px #ffffff",
+                        "color": "#333333",
+                    },
+                }
+            ],
+        }
+    ],
+    "legend": {"enabled": False},
+    "credits": {"enabled": False},
+}
+
+options_json = json.dumps(chart_options)
+
+# Download Highcharts JS, sankey module (dependency), and arc-diagram module
+cache_dir = Path("/tmp")
+urls = {
+    "highcharts": ("https://cdn.jsdelivr.net/npm/highcharts@11.4.8/highcharts.js", cache_dir / "highcharts.js"),
+    "sankey": ("https://cdn.jsdelivr.net/npm/highcharts@11.4.8/modules/sankey.js", cache_dir / "hc_sankey.js"),
+    "arcdiagram": (
+        "https://cdn.jsdelivr.net/npm/highcharts@11.4.8/modules/arc-diagram.js",
+        cache_dir / "hc_arc_diagram.js",
+    ),
+}
+js_scripts = {}
+for name, (url, cache_path) in urls.items():
+    if cache_path.exists() and cache_path.stat().st_size > 1000:
+        js_scripts[name] = cache_path.read_text(encoding="utf-8")
+    else:
+        for attempt in range(5):
+            try:
+                with urllib.request.urlopen(url, timeout=30) as resp:
+                    content = resp.read().decode("utf-8")
+                cache_path.write_text(content, encoding="utf-8")
+                js_scripts[name] = content
+                break
+            except urllib.error.HTTPError:
+                time.sleep(3 * (attempt + 1))
+highcharts_js = js_scripts["highcharts"]
+sankey_js = js_scripts["sankey"]
+arcdiagram_js = js_scripts["arcdiagram"]
+
+# Chart init JS: use formatter function to show only node names (no DOM manipulation)
+chart_init_js = f"""
+(function() {{
+    var opts = {options_json};
+    opts.series[0].dataLabels[0].formatter = function() {{
+        return this.point.isNode ? this.point.name : '';
+    }};
+    Highcharts.chart('container', opts);
+}})();
+"""
+
+# Build HTML with inline JS (no post-render DOM manipulation)
+html_content = f"""<!DOCTYPE html>
+<html>
+<head>
+    <meta charset="utf-8">
+    <script>{highcharts_js}</script>
+    <script>{sankey_js}</script>
+    <script>{arcdiagram_js}</script>
+</head>
+<body style="margin:0;">
+    <div id="container" style="width: 4800px; height: 2700px;"></div>
+    <script>{chart_init_js}</script>
+</body>
+</html>"""
+
+# Save interactive HTML version (CDN links for standalone use)
+standalone_html = f"""<!DOCTYPE html>
+<html>
+<head>
+    <meta charset="utf-8">
+    <script src="https://cdn.jsdelivr.net/npm/highcharts@11.4.8/highcharts.js"></script>
+    <script src="https://cdn.jsdelivr.net/npm/highcharts@11.4.8/modules/sankey.js"></script>
+    <script src="https://cdn.jsdelivr.net/npm/highcharts@11.4.8/modules/arc-diagram.js"></script>
+</head>
+<body style="margin:0; overflow:auto;">
+    <div id="container" style="width: 4800px; height: 2700px;"></div>
+    <script>{chart_init_js}</script>
+</body>
+</html>"""
+
+with open("plot.html", "w", encoding="utf-8") as f:
+    f.write(standalone_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
+
+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=4800,2900")
+
+driver = webdriver.Chrome(options=chrome_options)
+driver.get(f"file://{temp_path}")
+time.sleep(5)
+driver.save_screenshot("plot_raw.png")
+driver.quit()
+
+# Crop to exact 4800x2700 dimensions
+img = Image.open("plot_raw.png")
+img_cropped = img.crop((0, 0, 4800, 2700))
+img_cropped.save("plot.png")
+Path("plot_raw.png").unlink()
+
+Path(temp_path).unlink()