P6: convert monster to BaseDomain + BaseNodeAdapter + concern split

Refactor of monster to use the platform infrastructure (BaseDomain, BaseNodeAdapter,
ChildRouter, commandRegistry, statusBadge). Extracts concerns into
focused modules per .claude/refactor/MODULE_SPLIT.md generic template.
Tests stay green; CONTRACT.md generated; legacy aliases preserved.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/rain/rainAggregator.js

@@ -0,0 +1,58 @@
+'use strict';
+
+// Rain-data aggregator — sums per-location hourly precipitation, weighted
+// by per-hour probability, and stores both the raw and probability-weighted
+// values keyed by timestamp. sumRain/avgRain feed parameters.getRainIndex
+// which scales the predicted flow rate between nominalFlowMin and flowMax.
+
+class RainAggregator {
+  constructor({ logger } = {}) {
+    this.logger = logger;
+    this.aggregatedOutput = {};
+    this.sumRain = 0;
+    this.avgRain = 0;
+  }
+
+  // Returns the aggregated per-location object so callers can chain.
+  // Mutates this.aggregatedOutput / sumRain / avgRain in place.
+  update(value) {
+    if (!value) return this.aggregatedOutput;
+
+    const totalRaw = {};
+    const totalProb = {};
+    let numberOfLocations = 0;
+
+    Object.entries(value).forEach(([locationKey, location]) => {
+      numberOfLocations++;
+      const slot = (this.aggregatedOutput[locationKey] = {
+        tag: { latitude: location.latitude, longitude: location.longitude },
+        precipationRaw: {},
+        precipationProb: {},
+      });
+
+      Object.entries(location.hourly.time).forEach(([key, time]) => {
+        const currTimestamp = new Date(time).getTime();
+        let probability = 100;
+        if (typeof location.hourly.precipitation_probability !== 'undefined') {
+          probability = location.hourly.precipitation_probability[key];
+        }
+        if (probability > 0) probability /= 100;
+
+        if (totalRaw[currTimestamp] === undefined) totalRaw[currTimestamp] = 0;
+        if (totalProb[currTimestamp] === undefined) totalProb[currTimestamp] = 0;
+
+        totalRaw[currTimestamp] += location.hourly.precipitation[key];
+        totalProb[currTimestamp] += location.hourly.precipitation[key] * probability;
+
+        slot.precipationRaw[key] = { val: location.hourly.precipitation[key], time: currTimestamp };
+        slot.precipationProb[key] = { val: probability, time: currTimestamp };
+      });
+    });
+
+    this.sumRain = Object.values(totalProb).reduce((s, v) => s + v, 0);
+    this.avgRain = numberOfLocations > 0 ? this.sumRain / numberOfLocations : 0;
+    return this.aggregatedOutput;
+  }
+}
+
+module.exports = RainAggregator;