Add MVP ambient biome audio hook

AGRARIAN_DEVELOPMENT_ROADMAP.md

@@ -833,7 +833,7 @@ Target deliverable: A small group can join a server, spawn into one biome, gathe
 
 ## 0.1.P MVP Audio And Atmosphere
 
-- [ ] Add ambient biome audio.
+- [x] Add ambient biome audio. Extended the placed `AAgrarianWeatherAudioController` so its ambient component explicitly owns a Ground Zero coastal-scrub biome loop slot with separate day/night volume targets, keeping the current MVP silent until placeholder or final audio assets are assigned while giving the map a real ambient audio attachment point.
 - [ ] Add footstep placeholders.
 - [ ] Add gathering sounds.
 - [ ] Add fire sounds.

Docs/TechnicalDesignDocument.md

@@ -302,15 +302,19 @@ 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.
+First-pass biome and weather audio uses `AAgrarianWeatherAudioController`. The
+controller owns ambient, rain, wind, and storm audio components with assignable
+loop sound slots. The ambient component is explicitly the Ground Zero
+coastal-scrub biome bed through `BiomeAmbientLoopSound`, with separate day and
+night volume targets so the map can carry wind, surf, insects, distant birds, or
+other realistic low-level biome texture before final authored assets are
+available. 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.
 
 Campfires expose native extinguish logic through `AAgrarianCampfire::Extinguish`.
 Extinguishing clears remaining fuel, turns off replicated lit state, and reuses

Scripts/verify_ambient_biome_audio.py

@@ -0,0 +1,58 @@
+#!/usr/bin/env python3
+"""Verify the MVP ambient biome audio attachment point is wired."""
+
+from pathlib import Path
+
+
+ROOT = Path(__file__).resolve().parents[1]
+AUDIO_H = ROOT / "Source" / "AgrarianGame" / "AgrarianWeatherAudioController.h"
+AUDIO_CPP = ROOT / "Source" / "AgrarianGame" / "AgrarianWeatherAudioController.cpp"
+MAP_SETUP = ROOT / "Scripts" / "setup_ground_zero_demo_map.py"
+TDD = ROOT / "Docs" / "TechnicalDesignDocument.md"
+ROADMAP = ROOT / "AGRARIAN_DEVELOPMENT_ROADMAP.md"
+
+
+REQUIRED = {
+    AUDIO_H: [
+        "TObjectPtr<USoundBase> BiomeAmbientLoopSound;",
+        "float BiomeAmbientDayVolume",
+        "float BiomeAmbientNightVolume",
+        "TObjectPtr<UAudioComponent> AmbientAudio;",
+    ],
+    AUDIO_CPP: [
+        "BiomeAmbientLoopSound",
+        "AmbientAudio->SetSound(BiomeAmbientLoopSound)",
+        "FMath::Max(AmbientDayVolume, BiomeAmbientDayVolume)",
+        "FMath::Max(AmbientNightVolume, BiomeAmbientNightVolume)",
+    ],
+    MAP_SETUP: [
+        "AGR_DemoWeatherAudioController",
+        "unreal.AgrarianWeatherAudioController",
+    ],
+    TDD: [
+        "coastal-scrub biome bed",
+        "`BiomeAmbientLoopSound`",
+        "separate day and\nnight volume targets",
+    ],
+    ROADMAP: [
+        "[x] Add ambient biome audio.",
+    ],
+}
+
+
+def main() -> None:
+    missing = []
+    for path, snippets in REQUIRED.items():
+        text = path.read_text(encoding="utf-8")
+        for snippet in snippets:
+            if snippet not in text:
+                missing.append(f"{path.relative_to(ROOT)} missing {snippet!r}")
+
+    if missing:
+        raise SystemExit("FAILED: " + "; ".join(missing))
+
+    print("OK: ambient biome audio is wired through the placed weather audio controller.")
+
+
+if __name__ == "__main__":
+    main()

Source/AgrarianGame/AgrarianWeatherAudioController.cpp

@@ -83,7 +83,9 @@ void AAgrarianWeatherAudioController::RefreshWeatherAudio(float DeltaSeconds)
 		break;
 	}
 
-	const float TargetAmbientVolume = GameState->IsNight() ? AmbientNightVolume : AmbientDayVolume;
+	const float DayAmbient = FMath::Max(AmbientDayVolume, BiomeAmbientDayVolume);
+	const float NightAmbient = FMath::Max(AmbientNightVolume, BiomeAmbientNightVolume);
+	const float TargetAmbientVolume = GameState->IsNight() ? NightAmbient : DayAmbient;
 	const float InterpSpeed = FMath::Max(0.1f, VolumeInterpSpeed);
 	CurrentAmbientVolume = FMath::FInterpTo(CurrentAmbientVolume, TargetAmbientVolume, DeltaSeconds, InterpSpeed);
 	CurrentRainVolume = FMath::FInterpTo(CurrentRainVolume, TargetRainVolume, DeltaSeconds, InterpSpeed);
@@ -106,7 +108,11 @@ void AAgrarianWeatherAudioController::RefreshWeatherAudio(float DeltaSeconds)
 
 void AAgrarianWeatherAudioController::AssignConfiguredSounds()
 {
-	if (AmbientAudio && ClearAmbientSound)
+	if (AmbientAudio && BiomeAmbientLoopSound)
+	{
+		AmbientAudio->SetSound(BiomeAmbientLoopSound);
+	}
+	else if (AmbientAudio && ClearAmbientSound)
 	{
 		AmbientAudio->SetSound(ClearAmbientSound);
 	}

Source/AgrarianGame/AgrarianWeatherAudioController.h

@@ -40,6 +40,9 @@ public:
 	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "Agrarian|Weather Audio")
 	TObjectPtr<USoundBase> ClearAmbientSound;
 
+	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "Agrarian|Weather Audio|Biome")
+	TObjectPtr<USoundBase> BiomeAmbientLoopSound;
+
 	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "Agrarian|Weather Audio")
 	TObjectPtr<USoundBase> RainLoopSound;
 
@@ -58,6 +61,12 @@ public:
 	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "Agrarian|Weather Audio", meta = (ClampMin = "0.0", ClampMax = "1.0"))
 	float AmbientNightVolume = 0.22f;
 
+	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "Agrarian|Weather Audio|Biome", meta = (ClampMin = "0.0", ClampMax = "1.0"))
+	float BiomeAmbientDayVolume = 0.35f;
+
+	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "Agrarian|Weather Audio|Biome", meta = (ClampMin = "0.0", ClampMax = "1.0"))
+	float BiomeAmbientNightVolume = 0.22f;
+
 	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "Agrarian|Weather Audio", meta = (ClampMin = "0.0", ClampMax = "1.0"))
 	float MaxRainVolume = 0.8f;