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.

docs/api/openapi.yaml

@@ -4207,11 +4207,13 @@ paths:
         With `groupBy=day` on a cumulative type the rows are one sum per local day, and `limit` / `offset` page over
         those days; every returned day is complete, which is why `valueMin` / `valueMax` (a filter on single readings)
         are refused with 422 beside `groupBy=day`. `type=SLEEP_DURATION` returns one row per night, paged the same way
-        over nights; every night of the page has a row, and a day whose only sleep is daytime naps carries `value` 0
-        with its naps in `napCount` / `napAsleepMinutes`. Its `dayKey` is the same day `/api/sleep/night?date=` answers
-        for. On both, `meta.total` counts the days or nights in the filtered window. A day-sum page takes `limit` as
-        asked (up to the list's 5000); a sleep page holds at most 1000 nights, and `meta.limit` echoes the value
-        applied.
+        over nights; every night of the page has a row, and `value` is the day's time asleep, the main night plus its
+        naps (the same total `/api/measurements/series?kind=sleep` and the sleep score read), with the main night alone
+        in `mainAsleepMinutes` and the naps in `napCount` / `napAsleepMinutes`; a day whose only sleep is daytime naps
+        carries the naps' minutes and `mainAsleepMinutes: null`. Its `dayKey` is the same day `/api/sleep/night?date=`
+        answers for. On both, `meta.total` counts the days or nights in the filtered window. A day-sum page takes
+        `limit` as asked (up to the list's 5000); a sleep page holds at most 1000 nights, and `meta.limit` echoes the
+        value applied.
       parameters:
         - in: query
           name: type
@@ -4732,16 +4734,18 @@ paths:
         source's stage segments (each with an absolute start/end), the per-stage breakdown, asleep/in-bed/awake totals,
         the mid-sleep awakenings count, and same-wake-day naps surfaced separately. Session-clustered, keyed by the
         local wake day, collapsed to one source via the sleep priority ladder so two sources never overlay. `date`
-        omitted returns the most recent night holding sleep, however old. Any past date is answered, with no window cut.
-        A read-only view over existing per-stage SLEEP_DURATION rows — no schema, no new measurement type."
+        omitted returns the most recent night with a main sleep, however old; later days of naps alone are stepped over
+        and stay reachable by `date`. An account that has only ever napped gets its latest day of naps. Any past date is
+        answered, with no window cut. A read-only view over existing per-stage SLEEP_DURATION rows — no schema, no new
+        measurement type."
       parameters:
         - in: query
           name: date
           schema:
-            description: Wake-day key (YYYY-MM-DD). Omit for the most recent night.
+            description: Wake-day key (YYYY-MM-DD). Omit for the most recent night with a main sleep.
             type: string
             pattern: ^\d{4}-\d{2}-\d{2}$
-          description: Wake-day key (YYYY-MM-DD). Omit for the most recent night.
+          description: Wake-day key (YYYY-MM-DD). Omit for the most recent night with a main sleep.
       responses:
         "200":
           description: Reconstructed night.
@@ -46284,6 +46288,23 @@ components:
           type: integer
           minimum: -9007199254740991
           maximum: 9007199254740991
+        mainAsleepMinutes:
+          description: The main night's own time asleep in minutes; null on a day of naps alone. On a sleep row `value` is the
+            day's total, the main night plus its naps.
+          anyOf:
+            - type: integer
+              minimum: 0
+              maximum: 9007199254740991
+            - type: "null"
+        napCount:
+          description: Naps on the same wake day.
+          type: integer
+          minimum: 0
+          maximum: 9007199254740991
+        napAsleepMinutes:
+          description: Time asleep across those naps, in minutes.
+          type: number
+          minimum: 0
       required:
         - id
         - type
@@ -47108,6 +47129,23 @@ components:
           type: integer
           minimum: -9007199254740991
           maximum: 9007199254740991
+        mainAsleepMinutes:
+          description: The main night's own time asleep in minutes; null on a day of naps alone. On a sleep row `value` is the
+            day's total, the main night plus its naps.
+          anyOf:
+            - type: integer
+              minimum: 0
+              maximum: 9007199254740991
+            - type: "null"
+        napCount:
+          description: Naps on the same wake day.
+          type: integer
+          minimum: 0
+          maximum: 9007199254740991
+        napAsleepMinutes:
+          description: Time asleep across those naps, in minutes.
+          type: number
+          minimum: 0
       required:
         - id
         - type
@@ -47289,6 +47327,23 @@ components:
           type: integer
           minimum: -9007199254740991
           maximum: 9007199254740991
+        mainAsleepMinutes:
+          description: The main night's own time asleep in minutes; null on a day of naps alone. On a sleep row `value` is the
+            day's total, the main night plus its naps.
+          anyOf:
+            - type: integer
+              minimum: 0
+              maximum: 9007199254740991
+            - type: "null"
+        napCount:
+          description: Naps on the same wake day.
+          type: integer
+          minimum: 0
+          maximum: 9007199254740991
+        napAsleepMinutes:
+          description: Time asleep across those naps, in minutes.
+          type: number
+          minimum: 0
         status:
           type: string
           enum: