WIP: feat(scene) integrate beauty pass — shader water, building blockouts, wind, smoke, 6 textures

- Add 3 missing Terrain3D textures: Dirt Path (id=3), Riverbank Stone (id=4),
  Compacted Ground (id=5) with procedural albedo PNGs + generate tool
- Replace greybox river BoxMesh with animated vertex-displacement water shader
- Replace greybox waterfall BoxMesh with scrolling-UV waterfall shader
- Add WaterfallMist GPUParticles3D with upward drift and alpha fade
- Add wind vertex shader for tree canopies (sin-based, height-weighted sway)
- Replace StylizedTree.tscn with script-driven procedural tree supporting
  3 canopy color variants and position-based randomization
- Replace greybox house boxes with StylizedHouse (walls + pitched roof + door)
- Replace mill box with StylizedMill (body + roof + water wheel cylinder)
- Replace fortress box with FortressBlockout (keep + parapet + corner turret)
- Replace bridge box with BridgeBlockout (deck + pillar supports)
- Add ChimneySmoke GPUParticles3D on each house roof
- Height-snap buildings (fortress + village) to terrain surface in _ready()
- Update JajceWorld.tscn: remove all greybox landmark sub-resources, instance
  new scenes, keep terrain/navigation/sky/fog as-is
- Update scaffold test for new scene structure and beauty elements

world/jajce/materials/water.gdshader

@@ -0,0 +1,20 @@
+shader_type spatial;
+render_mode blend_mix, depth_draw_opaque, cull_back, diffuse_burley, specular_schlick_ggx;
+
+uniform float wave_strength : hint_range(0.0, 1.0) = 0.15;
+uniform float wave_speed : hint_range(0.0, 5.0) = 1.2;
+
+void vertex() {
+	vec3 pos = VERTEX;
+	float wave = sin(pos.z * 0.4 + TIME * wave_speed) * wave_strength;
+	pos.y += wave;
+	VERTEX = pos;
+}
+
+void fragment() {
+	ALBEDO = vec3(0.12, 0.39, 0.55);
+	METALLIC = 0.15;
+	ROUGHNESS = 0.1;
+	EMISSION = vec3(0.05, 0.19, 0.24) * 0.45;
+	ALPHA = 0.72;
+}