Derive glucose isSpotEstimate from reading density

Hard-coding isSpotEstimate: true mislabels a dense Nightscout CGM stream
(~288 readings/day) as a spot estimate and undersells the data in the
clinical panel and coach. Compute readings-per-day over the covered span
and treat the series as continuous below the spot caveat once it clears a
~hourly bar (24 readings/day); sparse spot fingersticks keep the caveat.
The panel only renders the spot-reading line when isSpotEstimate, and the
OpenAPI field relaxes from a literal-true to a boolean.

src/components/insights/glucose/glucose-clinical-panel.tsx

@@ -206,10 +206,15 @@ export function GlucoseClinicalPanel() {
           ) : null}
         </section>
 
-        {/* Spot-reading honesty caveat — always present. */}
-        <p className="text-muted-foreground/80 text-xs" data-slot="glucose-spot-caveat">
-          {t("insights.bloodGlucose.clinical.spotCaveat")}
-        </p>
+        {/* Spot-reading honesty caveat — only for sparse spot data. A dense
+            continuous stream (a CGM such as Nightscout) clears the density bar
+            and reports `isSpotEstimate: false`, so the caveat would undersell
+            the data. */}
+        {clinical.isSpotEstimate ? (
+          <p className="text-muted-foreground/80 text-xs" data-slot="glucose-spot-caveat">
+            {t("insights.bloodGlucose.clinical.spotCaveat")}
+          </p>
+        ) : null}
 
         {/* Advanced indices behind a disclosure. */}
         {clinical.advanced ? (