feat(store): recordTrain with pruning and getSummary

src/store.js

@@ -1,4 +1,4 @@
-import { parseTarget } from './pure.js';
+import { parseTarget, pruneHistory, summary as computeSummary } from './pure.js';
 
 const KEY_TARGETS = 'tat.targets';
 const KEY_HISTORY = 'tat.history';
@@ -78,4 +78,19 @@ export class Store {
     this.prefs.pos = { x: pos.x, y: pos.y };
     return this._saveJson(KEY_PREFS, this.prefs);
   }
+
+  recordTrain(attr, delta, ts = Date.now()) {
+    if (typeof delta !== 'number' || !Number.isFinite(delta) || delta <= 0) {
+      return false;
+    }
+    const list = this.history[attr] || [];
+    list.push({ ts, delta });
+    this.history[attr] = pruneHistory(list, ts);
+    return this._saveJson(KEY_HISTORY, this.history);
+  }
+
+  getSummary(attr, now = Date.now()) {
+    const list = this.history[attr] || [];
+    return computeSummary(list, now);
+  }
 }