fix(insights): stop making claims about today out of older readings

The hero line said a pulse was well above its 30-day average today. Nothing
had measured a pulse for five days. The day-signals card flagged the same
reading, and the baseline-drift card said the value was above the usual range,
present tense, on a day that held no reading at all.

One class, and it sits in the data preparation rather than in any of the
sentences. Each surface was handed "the freshest stored value" with no notion
of when it was taken, so each of them assumed now. The age was reachable — the
aggregates carry `newestDaysAgo` inside their coverage object — but it read as
a statistics footnote rather than as the fact that governs the tense of every
sentence about the metric, and none of the three consulted it.

A reading is material for a claim about today when it comes from today or from
yesterday. One day rather than zero: a vital taken at 23:40 and read at 00:10
is the same reading it was half an hour earlier. Two is not, because by then a
whole day has passed with nothing in it and the sentence would be describing a
gap.

The rule now lives beside the data. The vital deviations carry the age of the
reading they were computed from, and the two deterministic consumers apply it:
the day-signals flag counts only current vitals toward its count, and the
baseline-drift card surfaces only current deviations. Stale vitals stay in the
list with their age, so the anatomy view still shows them and nothing silently
disappears; the dated level shifts were never today claims and are untouched.

For the narrated surfaces the same fact is stamped onto every metric block of
the Coach snapshot before anything reads it, so the age travels with the
numbers into the hero, the briefing, the Coach reply and the retrieval tools
instead of each of them guessing. A block narrated off a stale series also
lands in the wide event, which is where it should have been visible all along.

src/components/insights/__tests__/coincident-deviation-card.test.tsx

@@ -37,6 +37,7 @@ function deviation(
     high: 62,
     outside,
     direction: outside ? "above" : "in",
+    daysAgo: 0,
   };
 }