feat(highcharts): implement mosaic-categorical (#11052)

## Implementation: `mosaic-categorical` - javascript/highcharts

Implements the **javascript/highcharts** version of
`mosaic-categorical`.

**File:**
`plots/mosaic-categorical/implementations/javascript/highcharts.js`

**Parent Issue:** #3650

---
:robot: *[impl-generate
workflow](https://github.com/MarkusNeusinger/anyplot/actions/runs/33597666721)*

---------

Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>
Co-authored-by: Markus Neusinger <2921697+MarkusNeusinger@users.noreply.github.com>

Author: github-actions[bot]

plots/mosaic-categorical/implementations/javascript/highcharts.js

@@ -0,0 +1,180 @@
+// anyplot.ai
+// mosaic-categorical: Mosaic Plot for Categorical Association Analysis
+// Library: highcharts 12.6.0 | JavaScript 22.23.2
+// Quality: 92/100 | Created: 2026-09-02
+
+const t = window.ANYPLOT_TOKENS;
+
+// --- Data (in-memory, deterministic) ----------------------------------------
+// Contingency table: performance rating counts by department.
+const departments = ["Engineering", "Sales", "Marketing", "Support"];
+const ratings = ["Exceeds", "Meets", "Below"];
+const counts = [
+  [42, 58, 10], // Engineering
+  [35, 70, 25], // Sales
+  [20, 45, 15], // Marketing
+  [15, 38, 12], // Support
+];
+
+const colTotals = counts.map((row) => row.reduce((a, b) => a + b, 0));
+const grandTotal = colTotals.reduce((a, b) => a + b, 0);
+
+// Column boundaries in raw-count data units — these back the real xAxis scale
+// (0..grandTotal) so tick centers and column widths both derive from it.
+let cum = 0;
+const colStart = [];
+const colEnd = [];
+colTotals.forEach((ct) => {
+  colStart.push(cum);
+  cum += ct;
+  colEnd.push(cum);
+});
+const colCenters = colStart.map((s, i) => (s + colEnd[i]) / 2);
+
+// Precomputed luminance-based text color per rating (a lookup, not a per-cell helper call).
+function luminance(hex) {
+  const r = parseInt(hex.slice(1, 3), 16);
+  const g = parseInt(hex.slice(3, 5), 16);
+  const b = parseInt(hex.slice(5, 7), 16);
+  return (0.299 * r + 0.587 * g + 0.114 * b) / 255;
+}
+const textColors = ratings.map((_, j) => (luminance(t.palette[j]) > 0.6 ? "#1A1A17" : "#FFFFFF"));
+
+// Standout cell for storytelling emphasis: department with the highest "Below" share.
+const belowIdx = ratings.length - 1;
+let standoutIdx = 0;
+let standoutRatio = -1;
+counts.forEach((row, i) => {
+  const ratio = row[belowIdx] / colTotals[i];
+  if (ratio > standoutRatio) {
+    standoutRatio = ratio;
+    standoutIdx = i;
+  }
+});
+
+const colGap = 6;
+const rowGap = 3;
+
+// --- Chart -------------------------------------------------------------------
+Highcharts.chart("container", {
+  chart: {
+    backgroundColor: "transparent",
+    animation: false,
+    style: { fontFamily: "inherit" },
+    events: {
+      load() {
+        const r = this.renderer;
+
+        // Draw on top of the real xAxis/yAxis coordinate system: Highcharts has
+        // already reserved space for the title, subtitle, axis titles/labels and
+        // legend, so this box is the actual plot area, not a hand-picked margin.
+        const plotLeftPx = this.plotLeft;
+        const plotTopPx = this.plotTop;
+        const plotWidthPx = this.plotWidth;
+        const plotHeightPx = this.plotHeight;
+
+        // Column x-boundaries: width proportional to department headcount share.
+        const availableWidth = plotWidthPx - (departments.length - 1) * colGap;
+        let cursorX = plotLeftPx;
+        const colX = [];
+        const colWidth = [];
+        departments.forEach((_, i) => {
+          const w = (colTotals[i] / grandTotal) * availableWidth;
+          colX.push(cursorX);
+          colWidth.push(w);
+          cursorX += w + colGap;
+        });
+
+        // Mosaic rectangles: column width ∝ department share, row height ∝ rating share.
+        departments.forEach((dept, i) => {
+          const availableHeight = plotHeightPx - (ratings.length - 1) * rowGap;
+          let cursorY = plotTopPx;
+          ratings.forEach((rating, j) => {
+            const cellHeight = (counts[i][j] / colTotals[i]) * availableHeight;
+            const isStandout = i === standoutIdx && j === belowIdx;
+            r.rect(colX[i], cursorY, colWidth[i], cellHeight, 2)
+              .attr({
+                fill: t.palette[j],
+                stroke: isStandout ? t.amber : t.pageBg,
+                "stroke-width": isStandout ? 3 : 2,
+              })
+              .add();
+
+            if (colWidth[i] > 46 && cellHeight > 28) {
+              r.text(String(counts[i][j]), colX[i] + colWidth[i] / 2, cursorY + cellHeight / 2 + 5)
+                .attr({ align: "center" })
+                .css({ color: textColors[j], fontSize: "14px", fontWeight: "600" })
+                .add();
+            }
+            cursorY += cellHeight + rowGap;
+          });
+        });
+      },
+    },
+  },
+  credits: { enabled: false },
+  colors: t.palette,
+  title: {
+    text: "mosaic-categorical · javascript · highcharts · anyplot.ai",
+    style: { color: t.ink, fontSize: "22px", fontWeight: "600" },
+  },
+  subtitle: {
+    text: `${departments[standoutIdx]} has the highest 'Below' share, at ${Math.round(standoutRatio * 100)}%`,
+    style: { color: t.inkSoft, fontSize: "14px" },
+  },
+  xAxis: {
+    type: "linear",
+    min: 0,
+    max: grandTotal,
+    tickPositions: colCenters,
+    lineWidth: 0,
+    tickLength: 0,
+    gridLineWidth: 0,
+    labels: {
+      formatter() {
+        return departments[colCenters.indexOf(this.value)] ?? "";
+      },
+      style: { color: t.inkSoft, fontSize: "14px" },
+    },
+    title: {
+      text: "Department  ·  column width ∝ headcount",
+      style: { color: t.inkSoft, fontSize: "16px" },
+    },
+  },
+  yAxis: {
+    type: "linear",
+    min: 0,
+    max: 100,
+    tickPositions: [0, 25, 50, 75, 100],
+    lineWidth: 0,
+    gridLineColor: t.grid,
+    labels: {
+      formatter() {
+        return `${this.value}%`;
+      },
+      style: { color: t.inkSoft, fontSize: "14px" },
+    },
+    title: {
+      text: "Rating share within department",
+      style: { color: t.inkSoft, fontSize: "16px" },
+    },
+  },
+  legend: {
+    enabled: true,
+    align: "right",
+    verticalAlign: "middle",
+    layout: "vertical",
+    title: { text: "Performance rating", style: { color: t.inkSoft, fontSize: "14px", fontWeight: "600" } },
+    itemStyle: { color: t.inkSoft, fontSize: "14px" },
+    itemHoverStyle: { color: t.ink },
+    symbolRadius: 2,
+  },
+  tooltip: { enabled: false },
+  plotOptions: { series: { animation: false, enableMouseTracking: false } },
+  series: ratings.map((rating, j) => ({
+    type: "column",
+    name: rating,
+    data: [],
+    color: t.palette[j],
+  })),
+});