fix(insights): unify sleep reconstruction and make WHOOP recovery canonical

Route the derived Sleep Score through the canonical night reconstruction
instead of its own UTC-day grouping, so a night logged by more than one
source is deduplicated to a single writer rather than summed. The score and
the readiness that folds it now read true per-night totals; multi-source
nights drop to their real figure. Emitted minutes and the night stage map
round to integers.

Resolve recovery to one canonical series — WHOOP-native when present, the
computed proxy as fallback — in the wellness reader, the doctor report, and
the coach snapshot, and stop presenting the proxy and the native score as two
numbers. A WHOOP-connected account's recovery now reads the native value on
the tile, the chart, and the printed report alike.

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

@@ -64,7 +64,14 @@ function serializeSession(s: SleepSession) {
     inBedMinutes: s.inBedMinutes === null ? null : Math.round(s.inBedMinutes),
     awakeMinutes: s.awakeMinutes === null ? null : Math.round(s.awakeMinutes),
     awakenings: s.awakenings,
-    stages: s.stages,
+    // iOS #18 — round the per-stage map too; the underlying totals sum
+    // second-precision segments and otherwise serialise as e.g. 88.4999.
+    stages: Object.fromEntries(
+      Object.entries(s.stages).map(([stage, minutes]) => [
+        stage,
+        Math.round(minutes),
+      ]),
+    ),
     segments: s.segments.map((seg) => ({
       stage: seg.stage,
       start: seg.start.toISOString(),

src/app/api/sync/changes/route.ts

@@ -319,6 +319,15 @@ export const GET = apiHandler(async (request: NextRequest) => {
         updatedAt: row.updatedAt.toISOString(),
       });
     } else {
+      // Every row carries its `source`. RECOVERY_SCORE is written by BOTH the
+      // WHOOP-native sync (`source = WHOOP`) and the COMPUTED proxy job
+      // (`source = COMPUTED`) for the same day; the client must resolve to ONE
+      // canonical recovery series — WHOOP wins when present, COMPUTED is the
+      // fallback — and never chart the proxy and the native value as two
+      // competing series. The feed faithfully mirrors both rows (a delta-sync
+      // mirror cannot drop a row mid-keyset without a tombstone); the
+      // canonical pick is the same WHOOP-over-COMPUTED rule the server's
+      // wellness tile + doctor PDF apply (`resolveCanonicalRecovery`).
       measurementUpserts.push({
         id: row.id,
         externalId: row.externalId,