fix(sleep): round night minute totals to whole numbers

`GET /api/sleep/night` summed second-precision stage rows into asleep /
awake totals and serialised them unrounded (e.g. 433.4999), which also
violated the OpenAPI integer contract. Round the present minute values;
`inBedMinutes` / `awakeMinutes` stay null when the night never saw that
stage.

src/app/api/sleep/night/__tests__/route.test.ts

@@ -103,6 +103,24 @@ describe("GET /api/sleep/night", () => {
     expect(core.end).toBe("2026-06-04T01:00:00.000Z");
   });
 
+  it("rounds asleep / awake minutes to whole numbers", async () => {
+    // iOS #18 — `asleepMinutesOf` / awake totals sum raw second-precision
+    // minute values, so a night sums to e.g. 433.4999; the serializer must
+    // emit whole minutes. CORE+DEEP = 433.4999 → 433; AWAKE 12.6 → 13.
+    vi.mocked(getSession).mockResolvedValue(SESSION_OK as never);
+    vi.mocked(prisma.measurement.findMany).mockResolvedValue([
+      stage("2026-06-04T03:00:00.000Z", "CORE", 300.25),
+      stage("2026-06-04T05:00:00.000Z", "DEEP", 133.2499),
+      stage("2026-06-04T05:10:00.000Z", "AWAKE", 12.6),
+    ] as never);
+    const res = await GET(req("date=2026-06-04"));
+    const body = await res.json();
+    expect(body.data.main.asleepMinutes).toBe(433);
+    expect(body.data.main.awakeMinutes).toBe(13);
+    expect(Number.isInteger(body.data.main.asleepMinutes)).toBe(true);
+    expect(Number.isInteger(body.data.main.awakeMinutes)).toBe(true);
+  });
+
   it("defaults to the most recent scorable night when date omitted", async () => {
     vi.mocked(getSession).mockResolvedValue(SESSION_OK as never);
     vi.mocked(prisma.measurement.findMany).mockResolvedValue([

src/app/api/sleep/night/route.ts

@@ -56,9 +56,13 @@ function serializeSession(s: SleepSession) {
     source: s.source,
     start: s.start.toISOString(),
     end: s.end.toISOString(),
-    asleepMinutes: s.asleepMinutes,
-    inBedMinutes: s.inBedMinutes,
-    awakeMinutes: s.awakeMinutes,
+    // iOS #18 — round to whole minutes; the underlying totals are summed from
+    // second-precision segments and otherwise serialise as e.g. 433.4999.
+    // `inBedMinutes` / `awakeMinutes` stay null when the night never saw that
+    // stage — rounding only the present values.
+    asleepMinutes: Math.round(s.asleepMinutes),
+    inBedMinutes: s.inBedMinutes === null ? null : Math.round(s.inBedMinutes),
+    awakeMinutes: s.awakeMinutes === null ? null : Math.round(s.awakeMinutes),
     awakenings: s.awakenings,
     stages: s.stages,
     segments: s.segments.map((seg) => ({