fix(sleep): one day total for every sleep reader, and the latest night is a night

A day's sleep is the main night plus its naps (daySleepMinutes). The
series, the sleep score and the composition already read it that way; the
sleep list, the CSV export and the correlation sleep channel read the main
night alone, so a day of naps listed as 0 h and an average over the list
counted it as a night without sleep. The list now carries the day total in
value and the main night alone in the new mainAsleepMinutes field; the nap
caption reads as included.

GET /api/sleep/night without a date answered the latest day holding any
sleep, so a nap after the last night left the hypnogram with no night to
draw. It now walks back to the latest night with a main sleep; nap days
stay reachable by date.

The SQL night page bounded a night by its asleep sessions only, so an
in-bed-only session of the same night fell outside a chunked read that the
one-night read counted. The span now covers every session of the night.

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

@@ -28,6 +28,17 @@ vi.mock("@/lib/modules/gate", () => ({
   requireModuleEnabled: vi.fn(async () => ({ enabled: true })),
 }));
 
+// The latest-night walk pages nights in SQL; its own behaviour is pinned by
+// the SQL parity integration suite. Here it is stubbed to a fixed day so the
+// route's "no date" arm can be read.
+vi.mock("@/lib/measurements/list/sleep-nights", async (importOriginal) => {
+  const actual =
+    await importOriginal<
+      typeof import("@/lib/measurements/list/sleep-nights")
+    >();
+  return { ...actual, latestMainSleepNight: vi.fn(async () => null) };
+});
+
 vi.mock("@/lib/db-compat", () => ({
   ensureDbCompatibility: vi.fn().mockResolvedValue(undefined),
 }));
@@ -49,6 +60,7 @@ vi.mock("next/headers", () => ({
 import { GET } from "../route";
 import { prisma } from "@/lib/db";
 import { getSession } from "@/lib/auth/session";
+import { latestMainSleepNight } from "@/lib/measurements/list/sleep-nights";
 
 const SESSION_OK = {
   session: { id: "sess-1", expiresAt: new Date(Date.now() + 3_600_000) },
@@ -133,15 +145,13 @@ describe("GET /api/sleep/night", () => {
     expect(Number.isInteger(body.data.main.awakeMinutes)).toBe(true);
   });
 
-  it("defaults to the most recent scorable night when date omitted", async () => {
+  it("defaults to the latest main night when date omitted", async () => {
     vi.mocked(getSession).mockResolvedValue(SESSION_OK as never);
     vi.mocked(prisma.measurement.findMany).mockResolvedValue([
       stage("2026-06-02T03:00:00.000Z", "CORE", 200),
       stage("2026-06-04T03:00:00.000Z", "CORE", 300),
     ] as never);
-    vi.mocked(prisma.measurement.findFirst).mockResolvedValue({
-      measuredAt: new Date("2026-06-04T03:00:00.000Z"),
-    } as never);
+    vi.mocked(latestMainSleepNight).mockResolvedValueOnce("2026-06-04");
     const res = await GET(req(""));
     const body = await res.json();
     expect(body.data.night).toBe("2026-06-04");

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

@@ -17,7 +17,9 @@
  * (WHOOP) — the client renders the hypnogram but labels it an approximate
  * layout. A real-series source (Apple Health / Withings / Fitbit) is false.
  *
- * `date` omitted → the most recent night that holds sleep, however old.
+ * `date` omitted → the most recent night with a main sleep, however old; a
+ * run of nap-only days since is stepped over (each stays reachable by its
+ * `date`). An account that has only ever napped gets its latest nap day.
  *
  * Only the stage rows within a day and a half of the night are read, as the
  * list's drill-down reads them (`readNightSessions`), so any past night is
@@ -39,7 +41,7 @@ import {
   type SleepSession,
 } from "@/lib/analytics/sleep-night";
 import {
-  latestSleepNight,
+  latestMainSleepNight,
   readNightSessions,
 } from "@/lib/measurements/list/sleep-nights";
 import { loadUserSourcePriority } from "@/lib/rollups/measurement-read";
@@ -131,7 +133,9 @@ export const GET = apiHandler(async (request: NextRequest) => {
   ]);
 
   const targetDay =
-    date ?? (await latestSleepNight(user.id, tz, priorityJson)) ?? undefined;
+    date ??
+    (await latestMainSleepNight(user.id, tz, priorityJson)) ??
+    undefined;
   const { main, naps } = targetDay
     ? pickMainNightAndNaps(
         (await readNightSessions(user.id, targetDay, tz, priorityJson))