feat(insights): add the same-time baseline for cumulative metrics

Compare today's running total at the last completed local hour against this
person's own typical total at that same hour, over a trailing four weeks of
stored intraday profiles. Same estimator as the vitals baseline — median for
the centre, median plus or minus k times MAD for the band — so a reader who
understands one understands the other.

It refuses to speak below fourteen usable days and says so through the
existing insufficient arm rather than a band built on three days. It ships no
projected day total: extrapolating a partial day is a guess, and this exists
to replace guesses.

Steps first; active energy, distance and flights ride the same engine.

src/components/insights/derived/standards.ts

@@ -178,4 +178,14 @@ export const METRIC_PROVENANCE: Record<DerivedMetricId, MetricProvenanceMeta> =
       },
       caveatKey: "insights.derived.composite.TRAJECTORY.caveat",
     },
+    SAME_TIME_BASELINE: {
+      methodKey: "insights.derived.composite.SAME_TIME_BASELINE.method",
+      standard: {
+        // Same robust median ± k·MAD estimator as the vitals baseline, applied
+        // to the window's totals at one local hour rather than to daily means.
+        name: "Leys et al. 2013, J. Exp. Soc. Psychol.",
+        url: "https://doi.org/10.1016/j.jesp.2013.03.013",
+      },
+      caveatKey: "insights.derived.composite.SAME_TIME_BASELINE.caveat",
+    },
   };