Add weather audio cues

Docs/TechnicalDesignDocument.md

@@ -164,6 +164,16 @@ the represented local day/night cycle and current weather without hard-coded
 static light settings. The Ground Zero map setup script places this controller
 and removes the earlier static demo sun/skylight/fog actors.
 
+First-pass weather audio uses `AAgrarianWeatherAudioController`. The controller
+owns ambient, rain, wind, and storm audio components with assignable loop sound
+slots. It reads replicated weather state, provider wind speed, provider cloud
+data, and local night/day state, then fades component volumes so rain, wind, and
+storm cues follow the same authoritative weather mapping used by temperature and
+lighting. The current MVP can ship without final sound assets because the
+controller is silent until loops are assigned; placeholder or final audio can be
+added by setting the exposed sound properties on the placed controller or a
+Blueprint child.
+
 The first real-weather adapter is `UAgrarianWeatherProviderSubsystem`. It uses
 Open-Meteo forecast requests keyed by tile center latitude/longitude, parses the
 current temperature, daily low/high, precipitation, wind, humidity, cloud cover,