feat(devops): separate public page server timing diagnostics

src/lib/performance-diagnostics.test.ts

@@ -85,3 +85,22 @@ it("does not change a completed snapshot when background work finishes", async (
 	await background;
 	expect(result.metrics.external.count).toBe(0);
 });
+
+it("reports timings on failure without replacing the application error", async () => {
+	const error = new Error("original");
+	let captured = 0;
+	await expect(
+		collectPerformance(
+			async () => {
+				await measureDependency("database", async () => {
+					throw error;
+				});
+			},
+			(metrics) => {
+				captured = metrics.database.errors;
+				throw Error("telemetry failure");
+			},
+		),
+	).rejects.toBe(error);
+	expect(captured).toBe(1);
+});