fix(ui): lift the remaining explainer prose out of muted

Residual grey-on-content sweep after the page-description lift:
multi-sentence explainer paragraphs are content and read in the
regular foreground, matching the metric sub-page explainer that set
the pattern — the labs biomarker and custom-metric detail leads, the
recovery metric and resilience explainers, and the onboarding
carousel/done-screen body copy. Muted stays reserved for meta:
timestamps, units, captions under a stat, one-sentence description
slots.

src/components/onboarding/done-screen.tsx

@@ -81,7 +81,7 @@ export function DoneScreen() {
         <p className="text-foreground text-sm font-medium">
           {t("onboarding.done.aiTitle")}
         </p>
-        <p className="text-muted-foreground text-sm leading-relaxed">
+        <p className="text-foreground text-sm leading-relaxed">
           {t("onboarding.done.aiBody")}
         </p>
         <Link

src/components/onboarding/welcome-carousel.tsx

@@ -211,7 +211,7 @@ export function WelcomeCarousel() {
               >
                 {t(slide.titleKey)}
               </h2>
-              <p className="text-muted-foreground text-sm leading-relaxed">
+              <p className="text-foreground text-sm leading-relaxed">
                 {t(slide.bodyKey)}
               </p>
             </article>
@@ -302,7 +302,7 @@ export function WelcomeCarousel() {
         />
         <label
           htmlFor={disclaimerId}
-          className="text-muted-foreground text-sm leading-relaxed"
+          className="text-foreground text-sm leading-relaxed"
         >
           {t("onboarding.disclaimer.acknowledge")}{" "}
           <Link