feat(pure): summary with today/week counts and per-day rate

src/pure.js

@@ -65,3 +65,41 @@ export function pruneHistory(entries, now = Date.now()) {
   const cutoff = now - THIRTY_DAYS_MS;
   return entries.filter((e) => e.ts > cutoff);
 }
+
+/**
+ * Summarise training history.
+ *
+ * @param {{ts:number, delta:number}[]} entries
+ * @param {number} [now] Reference time in ms (defaults to Date.now()).
+ * @returns {{trainsToday:number, sevenDayAvgPerDay:number, perDay:number}}
+ */
+export function summary(entries, now = Date.now()) {
+  if (entries.length === 0) {
+    return { trainsToday: 0, sevenDayAvgPerDay: 0, perDay: 0 };
+  }
+
+  const ONE_DAY = MS_PER_DAY;
+  const SEVEN_DAYS = 7 * MS_PER_DAY;
+
+  const todayCutoff = now - ONE_DAY;
+  const weekCutoff = now - SEVEN_DAYS;
+
+  let trainsToday = 0;
+  let trainsWeek = 0;
+  let latestDelta = 0;
+  let latestTs = -Infinity;
+
+  for (const e of entries) {
+    if (e.ts >= todayCutoff) trainsToday++;
+    if (e.ts >= weekCutoff) trainsWeek++;
+    if (e.ts > latestTs) {
+      latestTs = e.ts;
+      latestDelta = e.delta;
+    }
+  }
+
+  const sevenDayAvgPerDay = trainsWeek / 7;
+  const perDay = latestDelta > 0 ? Math.floor(sevenDayAvgPerDay * latestDelta) : 0;
+
+  return { trainsToday, sevenDayAvgPerDay, perDay };
+}