docs: add agent skill guides and update CMake build instructions

.agents/skills/vtk_visualization.md

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+# Skill: VTK Visualization Pipeline
+
+This skill defines how to bridge domain objects with the VTK 3D visualization layer.
+
+## Context
+- **Wrapper**: `Prop3D` (wraps a `vtkProp`).
+- **Mapping**: `Viewport` maintains `m_ObjectToProp3D` for synchronization.
+- **GUI Integration**: `QViewport` handles Qt events and selection signals.
+
+## Implementation Patterns
+
+### 1. Creating a Prop3D
+A `Prop3D` should wrap a domain object and update its visual state when the object changes.
+```cpp
+class MyProp3D : public Prop3D {
+public:
+    MyProp3D(MyObject* obj) : Prop3D(obj) {
+        // Connect domain updates to visual refreshes
+        uLib::Object::connect(obj, &Object::Updated, [this]() { this->SyncFromObject(); });
+        
+        // Expose properties to the VTK side-panel
+        ULIB_ACTIVATE_DISPLAY_PROPERTIES(*this)
+    }
+    
+    void SyncFromObject() {
+        // Update VTK actors/mappers from MyObject's properties
+    }
+};
+```
+
+### 2. Display Properties
+Use `serialize_display` to choose which properties of the domain object or the `Prop3D` itself are visible in the sliding "Display Properties" panel in `gcompose`.
+```cpp
+void serialize_display(Archive::display_properties_archive &ar) {
+    ar & boost::serialization::make_hrp("Opacity", m_Opacity);
+    ar & boost::serialization::make_hrp("Wireframe", m_Wireframe);
+}
+```
+
+### 3. Transformation Sync (TRS)
+Always synchronize the object's `trs` (Translate, Rotate, Scale) with the VTK actor's user transform.
+```cpp
+void UpdateTransform() {
+    auto matrix = GetContent()->GetTransform().GetMatrix();
+    m_Actor->SetUserMatrix(uLib::ToVtkMatrix(matrix));
+}
+```
+
+## Checklist
+- [ ] Does the `Prop3D` connect to the object's `Updated()` signal?
+- [ ] Are `ULIB_ACTIVATE_DISPLAY_PROPERTIES` and `serialize_display` implemented?
+- [ ] Is the transformation (TRS) correctly mapped to the VTK actor?