feat(api): explain dashboard chargeability by chapter

packages/api/src/__tests__/assistant-tools-dashboard-detail.test.ts

@@ -4,6 +4,7 @@ import { SystemRole } from "@capakraken/shared";
 import {
   createToolContext,
   executeTool,
+  getDashboardChargeabilityOverview,
   getDashboardDemand,
   getDashboardOverview,
   getDashboardPeakTimes,
@@ -139,6 +140,38 @@ describe("assistant dashboard tools detail aggregation", () => {
         },
       },
     ]);
+    vi.mocked(getDashboardChargeabilityOverview).mockResolvedValue({
+      rows: [
+        {
+          id: "res_1",
+          eid: "pparker",
+          displayName: "Peter Parker",
+          chapter: "Delivery",
+          chargeabilityTarget: 78,
+          actualChargeability: 70,
+          expectedChargeability: 76,
+          derivation: {
+            weeklyAvailabilityHours: 40,
+            baseWorkingDays: 22,
+            effectiveWorkingDayEquivalent: 21,
+            baseAvailableHours: 176,
+            effectiveAvailableHours: 168,
+            publicHolidayCount: 1,
+            publicHolidayWorkdayCount: 1,
+            publicHolidayHoursDeduction: 8,
+            absenceDayEquivalent: 0,
+            absenceHoursDeduction: 0,
+            actualBookedHours: 117.6,
+            expectedBookedHours: 127.7,
+            targetBookedHours: 131,
+            unassignedHours: 40.3,
+          },
+        },
+      ],
+      top: [],
+      watchlist: [],
+      month: "2026-03",
+    });
 
     const ctx = createToolContext(
       {
@@ -263,8 +296,28 @@ describe("assistant dashboard tools detail aggregation", () => {
       chargeabilityByChapter: [
         {
           chapter: "Delivery",
-          headcount: 4,
+          headcount: 1,
+          avgTargetPct: 78,
+          avgActualPct: 70,
+          avgExpectedPct: 76,
+          gapToTargetPct: 8,
           avgTarget: "78%",
+          avgActual: "70%",
+          avgExpected: "76%",
+          explainability: {
+            month: "2026-03",
+            resourceCount: 1,
+            derivedHeadcount: 1,
+            baseAvailableHours: 176,
+            effectiveAvailableHours: 168,
+            actualBookedHours: 117.6,
+            expectedBookedHours: 127.7,
+            targetBookedHours: 131,
+            publicHolidayHoursDeduction: 8,
+            absenceDayEquivalent: 0,
+            absenceHoursDeduction: 0,
+            unassignedHours: 40.3,
+          },
         },
       ],
     });