feat(illness): name the symptom curve in the recovery-gap card

When the logged symptom curve drives the recovery gap, the card names it
('you felt better N days before your logged symptoms eased') instead of
the vital-driven phrasing. Mirror the new gapDriverType and the return
track's adverse flag into the client DTO, and add the driver-aware copy
across all six locales.

src/components/illness/illness-correlation-card.tsx

@@ -44,6 +44,10 @@ function DeviationRow({ d }: { d: IllnessVitalDeviation }) {
 function CorrelationBody({ value }: { value: IllnessCorrelationValue }) {
   const { t } = useTranslations();
   const gap = value.recoveryGapDays;
+  // Driver-aware copy: when the user's logged symptom curve drove the gap, name
+  // the symptoms ("…before your symptoms eased"); otherwise the existing
+  // vital-driven phrasing. Clinically calm — observation, never prediction.
+  const symptomDriven = value.gapDriverType === "FUNCTIONAL_IMPACT";
 
   return (
     <div className="space-y-5">
@@ -71,11 +75,19 @@ function CorrelationBody({ value }: { value: IllnessCorrelationValue }) {
           </p>
           <p className="text-muted-foreground mt-1 text-sm">
             {gap > 0
-              ? t("illness.correlation.recoveryGapLag", { days: gap })
+              ? t(
+                  symptomDriven
+                    ? "illness.correlation.recoveryGapLagSymptom"
+                    : "illness.correlation.recoveryGapLag",
+                  { days: gap },
+                )
               : gap < 0
-                ? t("illness.correlation.recoveryGapLead", {
-                    days: Math.abs(gap),
-                  })
+                ? t(
+                    symptomDriven
+                      ? "illness.correlation.recoveryGapLeadSymptom"
+                      : "illness.correlation.recoveryGapLead",
+                    { days: Math.abs(gap) },
+                  )
                 : t("illness.correlation.recoveryGapSame")}
           </p>
         </div>

src/components/illness/types.ts

@@ -97,9 +97,11 @@ export interface IllnessVitalDeviation {
 }
 
 export interface IllnessVitalReturn {
+  /** A `MeasurementType`, or `"FUNCTIONAL_IMPACT"` for the symptom-burden track. */
   type: string;
   returnedDay: string | null;
   gapDays: number | null;
+  adverse: boolean;
 }
 
 export interface IllnessRedFlag {
@@ -117,6 +119,12 @@ export interface IllnessCorrelationValue {
   recoveryGapDays: number | null;
   adverseCoverageDays: number;
   feltBetterDay: string | null;
+  /**
+   * The metric that drove the headline gap — a `MeasurementType`,
+   * `"FUNCTIONAL_IMPACT"` (the symptom-burden track), or null. Drives the
+   * driver-aware recovery-gap copy.
+   */
+  gapDriverType: string | null;
   redFlags: IllnessRedFlag[];
 }