fix(labs): stop projecting lab trends from stale or short series

A marker whose newest reading is more than a year old is now reported
as of that reading (projection "stale"), with no exit date and no
already-outside verdict. The projection horizon is capped at the span
the readings cover, so a line is never carried further ahead than the
data reaches back. The detail read keeps the newest 2000 readings
rather than the oldest.

src/components/labs/__tests__/lab-trend-card.test.tsx

@@ -20,6 +20,7 @@ const OK: BiomarkerTrendDto = {
   pValue: 0.02,
   fittedNow: 130,
   asOf: "2026-10-21",
+  horizonYears: 3,
   projection: "exits",
   exitDate: "2027-11-02",
   exitBound: "high",
@@ -71,4 +72,25 @@ describe("<LabTrendCard>", () => {
     ).toBe("");
     expect(render(undefined)).toBe("");
   });
+
+  it("words a stale trend as of its newest reading, and a span-bound horizon", () => {
+    const stale = render({
+      ...OK,
+      asOf: "2026-01-10",
+      projection: "stale",
+      exitDate: null,
+      exitBound: null,
+    });
+    expect(stale).toContain('data-projection="stale"');
+    expect(stale).toContain("more than a year ago");
+    expect(stale).not.toContain("forecast");
+    const beyond = render({
+      ...OK,
+      horizonYears: 1.5,
+      projection: "beyond_horizon",
+      exitDate: null,
+      exitBound: null,
+    });
+    expect(beyond).toContain("for more than 1.5 years");
+  });
 });

src/components/labs/lab-trend-card.tsx

@@ -48,7 +48,15 @@ export function LabTrendCard({
         })
       : trend.projection === "no_band"
         ? null
-        : t(`labs.trend.projection.${trend.projection}`);
+        : trend.projection === "stale"
+          ? t("labs.trend.projection.stale", {
+              date: fmt.dateShortSmartCalendar(trend.lastAt),
+            })
+          : trend.projection === "beyond_horizon"
+            ? t("labs.trend.projection.beyond_horizon", {
+                years: fmt.number(trend.horizonYears, 1),
+              })
+            : t(`labs.trend.projection.${trend.projection}`);
 
   return (
     <Card data-slot="lab-trend">

src/components/labs/types.ts

@@ -125,13 +125,15 @@ export type BiomarkerTrendDto =
       pValue: number;
       fittedNow: number;
       asOf: string;
+      horizonYears: number;
       projection:
         | "exits"
         | "beyond_horizon"
         | "no_exit"
         | "already_outside"
         | "no_clear_trend"
-        | "no_band";
+        | "no_band"
+        | "stale";
       exitDate: string | null;
       exitBound: "low" | "high" | null;
     }