fix: remove duplicate zone weather, consolidate RNG, name star constants

- weather: remove duplicate setZoneWeather(15) for Dustwallow Marsh —
  second call silently overwrote the first with different parameters
- weather: replace duplicate static RNG in getRandomPosition() with
  shared weatherRng() to avoid redundant generator state
- starfield: extract day/night cycle thresholds into named constants
  (kDuskStart/kNightStart/kDawnStart/kDawnEnd/kFadeDuration)
- skybox: replace while-loop time wrapping with std::fmod — avoids
  O(n) iterations on large time jumps

src/rendering/skybox.cpp

@@ -202,10 +202,9 @@ void Skybox::update(float deltaTime) {
 }
 
 void Skybox::setTimeOfDay(float time) {
-    // Clamp to 0-24 range
-    while (time < 0.0f) time += 24.0f;
-    while (time >= 24.0f) time -= 24.0f;
-
+    // Wrap to [0, 24) range using fmod instead of iterative subtraction
+    time = std::fmod(time, 24.0f);
+    if (time < 0.0f) time += 24.0f;
     timeOfDay = time;
 }
 

src/rendering/starfield.cpp

@@ -13,6 +13,14 @@
 namespace wowee {
 namespace rendering {
 
+// Day/night cycle thresholds (hours, 24h clock) for star visibility.
+// Stars fade in over 2 hours at dusk, stay full during night, fade out at dawn.
+static constexpr float kDuskStart = 18.0f;  // stars begin fading in
+static constexpr float kNightStart = 20.0f; // full star visibility
+static constexpr float kDawnStart = 4.0f;   // stars begin fading out
+static constexpr float kDawnEnd = 6.0f;     // stars fully gone
+static constexpr float kFadeDuration = 2.0f;
+
 StarField::StarField() = default;
 
 StarField::~StarField() {
@@ -303,22 +311,20 @@ void StarField::destroyStarBuffers() {
 }
 
 float StarField::getStarIntensity(float timeOfDay) const {
-    // Full night: 20:00–4:00
-    if (timeOfDay >= 20.0f || timeOfDay < 4.0f) {
+    // Full night
+    if (timeOfDay >= kNightStart || timeOfDay < kDawnStart) {
         return 1.0f;
     }
-    // Fade in at dusk: 18:00–20:00
-    else if (timeOfDay >= 18.0f && timeOfDay < 20.0f) {
-        return (timeOfDay - 18.0f) / 2.0f;  // 0 → 1 over 2 hours
+    // Fade in at dusk
+    if (timeOfDay >= kDuskStart) {
+        return (timeOfDay - kDuskStart) / kFadeDuration;
     }
-    // Fade out at dawn: 4:00–6:00
-    else if (timeOfDay >= 4.0f && timeOfDay < 6.0f) {
-        return 1.0f - (timeOfDay - 4.0f) / 2.0f;  // 1 → 0 over 2 hours
+    // Fade out at dawn
+    if (timeOfDay < kDawnEnd) {
+        return 1.0f - (timeOfDay - kDawnStart) / kFadeDuration;
     }
     // Daytime: no stars
-    else {
-        return 0.0f;
-    }
+    return 0.0f;
 }
 
 } // namespace rendering

src/rendering/weather.cpp

@@ -353,12 +353,11 @@ void Weather::resetParticles(const Camera& camera) {
 }
 
 glm::vec3 Weather::getRandomPosition(const glm::vec3& center) const {
-    static std::random_device rd;
-    static std::mt19937 gen(rd());
+    // Reuse the shared weather RNG to avoid duplicate generator state
     static std::uniform_real_distribution<float> dist(-1.0f, 1.0f);
 
-    float x = center.x + dist(gen) * SPAWN_VOLUME_SIZE;
-    float z = center.z + dist(gen) * SPAWN_VOLUME_SIZE;
+    float x = center.x + dist(weatherRng()) * SPAWN_VOLUME_SIZE;
+    float z = center.z + dist(weatherRng()) * SPAWN_VOLUME_SIZE;
     float y = center.y;
 
     return glm::vec3(x, y, z);
@@ -440,7 +439,6 @@ void Weather::initializeZoneWeatherDefaults() {
     setZoneWeather(148,  Type::RAIN, 0.1f, 0.4f, 0.15f);  // Darkshore
     setZoneWeather(331,  Type::RAIN, 0.1f, 0.3f, 0.1f);   // Ashenvale
     setZoneWeather(405,  Type::RAIN, 0.1f, 0.3f, 0.1f);   // Desolace
-    setZoneWeather(15,   Type::RAIN, 0.2f, 0.5f, 0.2f);   // Dustwallow Marsh
     setZoneWeather(490,  Type::RAIN, 0.1f, 0.4f, 0.15f);  // Un'Goro Crater
     setZoneWeather(493,  Type::RAIN, 0.1f, 0.3f, 0.1f);   // Moonglade