docs(coach): keep the labs block note to its old length

src/lib/ai/coach/snapshot.ts

@@ -666,10 +666,9 @@ async function buildCoachSnapshotImpl(
 
   // v1.18.11 (#65) — lab-result context. Like illness it is CONTEXT, not a
   // scope-gated metric: attached without a `registerBlock` so the budget
-  // degrader never sheds it. The helper is module-gated internally: with the
-  // labs module off it reads nothing and answers null. The block carries the
-  // latest resolved reading per biomarker (whole record or the lookback limit,
-  // capped) so the Coach can answer "what was my LDL".
+  // degrader never sheds it. Module-gated inside: with Labs off it reads
+  // nothing. It carries the latest reading per biomarker (whole record or the
+  // lookback limit, capped) so the Coach can answer "what was my LDL".
   const labsBlockPromise = buildLabsSnapshotBlock(userId, now, reach);
 
   // v1.38 — doctor-visit context. Like illness/labs it is attempted always (a