feat(highcharts): implement crossword-basic (#3875)

## Implementation: `crossword-basic` - highcharts

Implements the **highcharts** version of `crossword-basic`.

**File:** `plots/crossword-basic/implementations/highcharts.py`

**Parent Issue:** #3805

---
:robot: *[impl-generate
workflow](https://github.com/MarkusNeusinger/pyplots/actions/runs/21048827576)*

---------

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

Author: github-actions[bot]

plots/crossword-basic/implementations/highcharts.py

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+""" pyplots.ai
+crossword-basic: Crossword Puzzle Grid
+Library: highcharts unknown | Python 3.13.11
+Quality: 91/100 | Created: 2026-01-15
+"""
+
+import tempfile
+import time
+import urllib.request
+from pathlib import Path
+
+import numpy as np
+from highcharts_core.chart import Chart
+from highcharts_core.options import HighchartsOptions
+from highcharts_core.options.series.heatmap import HeatmapSeries
+from selenium import webdriver
+from selenium.webdriver.chrome.options import Options
+
+
+# Data - Create a 15x15 crossword grid with 180-degree rotational symmetry
+np.random.seed(42)
+grid_size = 15
+
+# Generate symmetric black cell pattern (1 = black/blocked, 0 = white/entry)
+grid = np.zeros((grid_size, grid_size), dtype=int)
+
+# Define black cells for one half (will be mirrored for symmetry)
+black_cells = [
+    (0, 4),
+    (0, 10),
+    (1, 4),
+    (1, 10),
+    (2, 7),
+    (3, 0),
+    (3, 5),
+    (3, 9),
+    (4, 3),
+    (4, 8),
+    (4, 13),
+    (5, 6),
+    (5, 11),
+    (6, 1),
+    (6, 2),
+    (6, 10),
+    (6, 14),
+    (7, 7),
+]
+
+# Place black cells with 180-degree symmetry
+for r, c in black_cells:
+    grid[r, c] = 1
+    grid[grid_size - 1 - r, grid_size - 1 - c] = 1
+
+# Calculate clue numbers - number cells that start words (across or down)
+numbers = {}
+clue_num = 1
+for r in range(grid_size):
+    for c in range(grid_size):
+        if grid[r, c] == 1:
+            continue
+        starts_across = (c == 0 or grid[r, c - 1] == 1) and (c < grid_size - 1 and grid[r, c + 1] == 0)
+        starts_down = (r == 0 or grid[r - 1, c] == 1) and (r < grid_size - 1 and grid[r + 1, c] == 0)
+        if starts_across or starts_down:
+            numbers[(r, c)] = clue_num
+            clue_num += 1
+
+# Prepare heatmap data - black cells = 1, white cells = 0
+heatmap_data = []
+for r in range(grid_size):
+    for c in range(grid_size):
+        heatmap_data.append([c, grid_size - 1 - r, int(grid[r, c])])
+
+# Create chart
+chart = Chart(container="container")
+chart.options = HighchartsOptions()
+
+# Chart configuration
+chart.options.chart = {
+    "type": "heatmap",
+    "width": 3600,
+    "height": 3600,
+    "backgroundColor": "#ffffff",
+    "marginTop": 120,
+    "marginBottom": 100,
+    "marginLeft": 100,
+    "marginRight": 100,
+}
+
+# Title
+chart.options.title = {
+    "text": "crossword-basic · highcharts · pyplots.ai",
+    "style": {"fontSize": "48px", "fontWeight": "bold"},
+}
+
+# Remove colorAxis legend
+chart.options.color_axis = {"min": 0, "max": 1, "stops": [[0, "#ffffff"], [1, "#000000"]], "visible": False}
+
+# X-axis (columns 1-15)
+chart.options.x_axis = {
+    "categories": [str(i + 1) for i in range(grid_size)],
+    "title": {"text": None},
+    "labels": {"style": {"fontSize": "28px"}},
+    "lineWidth": 2,
+    "lineColor": "#000000",
+    "tickWidth": 0,
+    "tickLength": 0,
+    "startOnTick": False,
+    "endOnTick": False,
+}
+
+# Y-axis (rows A-O)
+row_labels = [chr(65 + i) for i in range(grid_size)]
+chart.options.y_axis = {
+    "categories": list(reversed(row_labels)),
+    "title": {"text": None},
+    "labels": {"style": {"fontSize": "28px"}},
+    "lineWidth": 2,
+    "lineColor": "#000000",
+    "tickWidth": 0,
+    "tickLength": 0,
+    "startOnTick": False,
+    "endOnTick": False,
+    "reversed": False,
+}
+
+# Legend disabled
+chart.options.legend = {"enabled": False}
+
+# Create heatmap series
+series = HeatmapSeries()
+series.name = "Grid"
+series.data = heatmap_data
+series.border_width = 2
+series.border_color = "#000000"
+series.data_labels = {"enabled": False}
+
+chart.add_series(series)
+
+# Add clue numbers as annotations
+annotations = []
+for (r, c), num in numbers.items():
+    annotations.append(
+        {
+            "point": {"x": c, "y": grid_size - 1 - r, "xAxis": 0, "yAxis": 0},
+            "text": str(num),
+            "align": "left",
+            "verticalAlign": "top",
+            "x": -85,
+            "y": -75,
+            "style": {"fontSize": "28px", "fontWeight": "bold", "color": "#000000"},
+            "backgroundColor": "transparent",
+            "borderWidth": 0,
+            "shadow": False,
+        }
+    )
+
+chart.options.annotations = [{"labels": annotations, "draggable": ""}]
+
+# Plot options for heatmap - ensure all cells have visible borders
+chart.options.plot_options = {
+    "heatmap": {
+        "borderWidth": 3,
+        "borderColor": "#333333",
+        "dataLabels": {"enabled": False},
+        "colsize": 1,
+        "rowsize": 1,
+    }
+}
+
+# Download Highcharts JS and heatmap module
+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")
+
+heatmap_url = "https://code.highcharts.com/modules/heatmap.js"
+with urllib.request.urlopen(heatmap_url, timeout=30) as response:
+    heatmap_js = response.read().decode("utf-8")
+
+annotations_url = "https://code.highcharts.com/modules/annotations.js"
+with urllib.request.urlopen(annotations_url, timeout=30) as response:
+    annotations_js = response.read().decode("utf-8")
+
+# Generate HTML with inline scripts
+html_str = chart.to_js_literal()
+html_content = f"""<!DOCTYPE html>
+<html>
+<head>
+    <meta charset="utf-8">
+    <script>{highcharts_js}</script>
+    <script>{heatmap_js}</script>
+    <script>{annotations_js}</script>
+</head>
+<body style="margin:0;">
+    <div id="container" style="width: 3600px; height: 3600px;"></div>
+    <script>{html_str}</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
+
+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=3600,3600")
+
+driver = webdriver.Chrome(options=chrome_options)
+driver.get(f"file://{temp_path}")
+time.sleep(5)
+driver.save_screenshot("plot.png")
+driver.quit()
+
+Path(temp_path).unlink()
+
+# Also save HTML for interactive version
+html_output = f"""<!DOCTYPE html>
+<html>
+<head>
+    <meta charset="utf-8">
+    <script src="https://code.highcharts.com/highcharts.js"></script>
+    <script src="https://code.highcharts.com/modules/heatmap.js"></script>
+    <script src="https://code.highcharts.com/modules/annotations.js"></script>
+</head>
+<body style="margin:0;">
+    <div id="container" style="width: 100%; height: 100vh;"></div>
+    <script>{html_str}</script>
+</body>
+</html>"""
+with open("plot.html", "w", encoding="utf-8") as f:
+    f.write(html_output)