- WaterBody.tscn, WaterfallBody.tscn: gdshader files were referenced
with type="Material" instead of type="Shader". Wrapped each
shader in a ShaderMaterial sub-resource so Godot can load them.
- ChimneySmoke.tscn: reordered sub-resources so StandardMaterial3D
is defined before QuadMesh that references it.
- WaterfallMist.tscn: fixed node type GpuParticles3D -> GPUParticles3D
(case-sensitive class name in Godot 4.7).
- jajce_world.gd: added explicit Vector3 type annotation to fix
'Cannot infer the type of pos variable' parse error.
- main.tscn.uid: created missing UID mapping file. The scene header
declared uid="uid://rs3hv73svbpa" but no .uid file existed,
causing Godot to reject the scene as unsupported format.
