Add animation controller system, material assets and skeleton visualization

- .animctrl state machine asset (params/transitions/blend trees, 1D+2D
  directional blending) with Unity Animator-style editor panel: state
  list, transitions, params, directional pad preview driving live
  CrossFade on the selected entity
- Split animation evaluation out of SceneRenderer into
  AnimationSystem/AnimationEvaluator; skin palettes with rest-pose
  fallback and blend-weight epsilon filtering
- MaterialAsset (.material) with reload-safe preview tile pool
  (DropMaterial clears dirty refs before instance destruction)
- EditorGizmoPass skeleton wires + viewport joint overlay; camera
  projection rework (baked Vulkan Y-flip, ortho support)
- Editor/game build split via HELLOVULKAN_EDITOR option

shaders/gizmo_pick.frag

@@ -0,0 +1,12 @@
+#version 450
+
+// Editor gizmo 拾取片元：实体 id 原样写 R32Uint（与 hitproxy.frag 同
+// 语义）。flat = 无插值，像素值即命中图元的实体位模式。
+
+layout(location = 0) flat in uint inEntityId;
+
+layout(location = 0) out uvec4 outColor;
+
+void main() {
+    outColor = uvec4(inEntityId, 0u, 0u, 0u);
+}