[FIX] charts: truncate radar chart labels correctly

Before this commit:
- Radar chart point labels were truncated incorrectly because Chart.js
  passes extra arguments (label, index, labels) to the callback.
- As a result, truncateLabel received the index as maxLen and applied
  unnecessary truncation.

After this commit:
- The callback now wraps truncateLabel to pass only the label string.
- This ensures long labels are truncated with ellipsis and short labels
  remain unchanged.

closes #7178

Task: 5078858
X-original-commit: b2aec82
Signed-off-by: Adrien Minne (adrm) <adrm@odoo.com>
Signed-off-by: Ronakkumar Mukeshbhai Bharadiya (rmbh) <rmbh@odoo.com>

Author: rmbh-odoo

src/helpers/figures/charts/runtime/chartjs_scales.ts

@@ -226,7 +226,7 @@ export function getRadarChartScales(
       },
       pointLabels: {
         color: chartFontColor(definition.background),
-        callback: truncateLabel,
+        callback: (label: string) => truncateLabel(label),
       },
       suggestedMin: minValue < 0 ? minValue - 1 : 0,
     },

tests/figures/chart/radar_chart_plugin.test.ts

@@ -148,6 +148,17 @@ describe("radar chart", () => {
     const runtime = model.getters.getChartRuntime("chartId") as RadarChartRuntime;
     expect(runtime.chartJsConfig.options?.scales?.r?.suggestedMin).toBe(-8);
   });
+
+  test("Radar chart point labels are truncated properly", () => {
+    const model = new Model();
+    createRadarChart(model, { dataSets: [{ dataRange: "A1:A2" }] }, "chartId");
+    const runtime = model.getters.getChartRuntime("chartId") as RadarChartRuntime;
+    const callback = (runtime.chartJsConfig.options?.scales?.r as any)?.pointLabels
+      ?.callback as Function;
+
+    expect(callback("short", 0)).toBe("short");
+    expect(callback("very very long label of radar", 1)).toBe("very very long label…");
+  });
 });
 
 test("Humanization is taken into account for the axis ticks of a radar chart", async () => {