fix(weather): keep absent observations unknown instead of reporting clear skies

src/data/weather-missing-observations.test.mjs

@@ -0,0 +1,20 @@
+import test from 'node:test';
+import assert from 'node:assert/strict';
+import { normalizeRegionalWeather, weatherCodeLabel } from './regionalModel.js';
+test('missing weather observations never assert clear conditions', () => {
+  for (const value of [null, undefined, '', ' ', false, true]) {
+    assert.equal(weatherCodeLabel(value), 'CONDITIONS UNKNOWN');
+    assert.equal(
+      normalizeRegionalWeather({ current: { temperature_2m: value } }),
+      null,
+    );
+  }
+  assert.equal(weatherCodeLabel(0), 'CLEAR');
+  assert.equal(weatherCodeLabel('0'), 'CLEAR');
+  const record = normalizeRegionalWeather({
+    current: { temperature_2m: 0, weather_code: null, wind_speed_10m: false },
+  });
+  assert.equal(record.temperatureC, 0);
+  assert.equal(record.weatherCode, null);
+  assert.equal(record.windKph, null);
+});