Show configured metrics retention (Refs #141)

tests/unit/metrics.test.ts

@@ -439,6 +439,23 @@ describe('historical metrics', () => {
         expect(result.summary.playerHours * 3600).toBeCloseTo(30);
     });
 
+    it('updates retention in page loads and refreshes without new samples or cache expiry', async () => {
+        const { fleetSettings, saveFleetSettings } =
+            await import('../../src/lib/server/settings.js');
+        const { GET } = await import('../../src/routes/api/metrics/+server.js');
+        const { load } = await import('../../src/routes/metrics/+page.server.js');
+        vi.spyOn(Date, 'now').mockReturnValue(Date.UTC(2026, 9, 10, 12));
+        const url = new URL('http://localhost/metrics?days=7');
+        const pageData = () => load({ url } as Parameters<typeof load>[0]);
+        expect(await pageData()).toMatchObject({ metricsKeepDays: 31 });
+        for (const metricsKeepDays of [90, 0, 1]) {
+            saveFleetSettings({ ...fleetSettings(), metricsKeepDays });
+            const payload = await (await GET({ url })).json();
+            expect(payload.metricsKeepDays).toBe(metricsKeepDays);
+            expect(payload).toEqual(await pageData());
+        }
+    });
+
     it('shares the range parser and response contract between SSR and the uncached refresh endpoint', async () => {
         const { recordMetrics } = await import('../../src/lib/server/fleet/metrics.js');
         const { GET } = await import('../../src/routes/api/metrics/+server.js');