feat(insights): make sleep debt a configurable source ladder with a computed explainer

Generalise sleep debt onto the existing per-metric source-priority picker
(a new sleepDebt ladder, native-above-computed, default WHOOP > Oura > Polar >
computed) instead of assuming one provider. The rhythm read resolves the active
source off the ladder and carries it on the DTO; when the active source is our
own COMPUTED engine — every user today, since no provider ships a native
sleep-debt balance — the Sleep page explains what the figure means and that it
differs from a wearable's native number. The computed model itself is unchanged
and correct (a short rolling balance of need minus sleep, surplus-credited);
only stale comments that still referenced the old 14-night window are corrected.

src/components/insights/sleep/__tests__/chronotype-section.test.tsx

@@ -39,6 +39,7 @@ const READY_DTO: SleepRhythmDto = {
     nightsCounted: 10,
     windowNights: 14,
     nightsUntilReady: 0,
+    source: "COMPUTED",
   },
   chronotype: {
     state: "ready",

src/components/insights/sleep/__tests__/sleep-rhythm-cards.test.tsx

@@ -23,6 +23,7 @@ const PARTIAL_DEBT: SleepDebtDto = {
   nightsCounted: 3,
   windowNights: 5,
   nightsUntilReady: 1,
+  source: "COMPUTED",
 };
 
 const READY_DEBT: SleepDebtDto = {
@@ -32,6 +33,7 @@ const READY_DEBT: SleepDebtDto = {
   nightsCounted: 5,
   windowNights: 5,
   nightsUntilReady: 0,
+  source: "COMPUTED",
 };
 
 const LEARNING_CHRONO: ChronotypeDto = {

src/components/insights/sleep/__tests__/sleep-rhythm-section.test.tsx

@@ -47,6 +47,7 @@ const READY_DTO: SleepRhythmDto = {
     nightsCounted: 5,
     windowNights: 5,
     nightsUntilReady: 0,
+    source: "COMPUTED",
   },
   chronotype: {
     state: "ready",

src/components/insights/sleep/sleep-debt-card.tsx

@@ -4,6 +4,7 @@ import { Moon } from "lucide-react";
 
 import { useTranslations } from "@/lib/i18n/context";
 import { Card, CardContent, CardHeader, CardTitle } from "@/components/ui/card";
+import { InfoHint } from "@/components/ui/info-hint";
 import { LearningGate } from "@/components/ui/learning-gate";
 import type { SleepDebtDto } from "./use-sleep-rhythm";
 
@@ -37,6 +38,13 @@ export function SleepDebtCard({ debt }: { debt: SleepDebtDto }) {
             <CardTitle className="text-base font-semibold">
               {t("insights.sleep.debt.title")}
             </CardTitle>
+            {/* v1.25.0 — when the active source on the user's sleep-debt ladder
+                is our own COMPUTED engine (every user today, until a provider
+                ships a native debt), explain what the figure means and that it
+                differs from a wearable's native number. */}
+            {debt.source === "COMPUTED" ? (
+              <InfoHint label={t("insights.sleep.debt.computedInfo")} />
+            ) : null}
           </div>
         </CardHeader>
         <CardContent>

src/components/settings/sources-section.tsx

@@ -89,6 +89,8 @@ const METRIC_LABEL_KEYS: Record<SourcePriorityMetricKey, string> = {
   recovery: "settings.sections.sources.metrics.recovery",
   // v1.18.10 I-5 — native-vs-derived stress ladder.
   stress: "settings.sections.sources.metrics.stress",
+  // v1.25.0 — native-vs-computed sleep-debt ladder.
+  sleepDebt: "settings.sections.sources.metrics.sleepDebt",
 };
 
 const SOURCE_LABEL_KEYS: Record<string, string> = {