World: flora feel fix — kill double-animation (root sway off, shader wind is the idle motion) + thin flowers

Operator: base flora too dense + "the waving/shader doesn't look great".
Diagnosis: EVERY Synty flora prop (both biomes) uses the Synty/Foliage
VERTEX-wind shader — the transform root-tilt sway has been double-animating
all flora since 1.5, and ground-flush carpet props (Flowers_Flat,
Grass_*_Plane) visibly lift their edges when tilted.

- AmbientMotionConfig.SwayEnabled -> false (code default + the serialized
  scene value): idle motion = the authored per-vertex shader wind (tips bend,
  bases planted). Knob kept for A/B; walk-through RUSTLE stays as the
  reactive layer the shader can't provide.
- AmbientMotionSystem: flat carpet props excluded from the flora cache
  entirely — no tilt even from rustle.
- Flower density thinned deterministically: Flowers_Flat keep 40%,
  Wildflowers/Sunflowers keep 50%, center (r<13) thinned harder (x0.6) —
  17/38 drifts off; play/build area reads clear, flowers become ring accents.

Console clean; sway/rustle knobs remain live-tunable in the scene.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Assets/_Project/Scripts/Client/Presentation/AmbientMotionConfig.cs

@@ -26,8 +26,9 @@ namespace ProjectM.Client
         public Color BlightSporeColor = new Color(0.72f, 0.50f, 0.85f, 0.33f);
         public Vector3 AridWind = new Vector3(2.2f, -0.15f, 0.5f);
 
-        [Header("Idle foliage sway (flora prop roots within view of the camera)")]
-        public bool SwayEnabled = true;
+        [Header("Idle foliage sway (root tilt) — OFF by default since 1.5b: ALL Synty flora uses the Synty/Foliage")]
+        [Header("VERTEX-wind shader, so root tilt double-animates. Keep for A/B; rustle below stays the reactive layer.")]
+        public bool SwayEnabled = false;
         [Min(1f)] public float SwayRadius = 30f;
         [Min(0f)] public float SwayAmpDeg = 1.4f;
         [Min(0.05f)] public float SwayHz = 0.8f;