normalizers/nws: add NWS alerts normalizer and canonical alert mapping
- Introduce AlertsNormalizer to convert Raw NWS Alerts (SchemaRawNWSAlertsV1)
into canonical WeatherAlert runs (SchemaWeatherAlertV1)
- Add minimal NWS alerts response/types to support GeoJSON FeatureCollection parsing
- Map NWS alert properties (event, headline, severity, timing, area, references)
into model.WeatherAlert with best-effort timestamp handling
- Establish clear AsOf / EffectiveAt policy for alert runs to support stable
deduplication and snapshot semantics
- Register the new alerts normalizer alongside existing NWS observation and
forecast normalizers
Eric Rakestraw
00e811f8f7