Updated AnimationTree component to use Animation Tree Registry

AGENTS.md

@@ -229,6 +229,8 @@ The editor/game mode executable adds its own ECS modules:
 | EditorUISystem | ImGui property panels and scene management |
 | ProceduralTextureSystem | Runtime procedural texture generation |
 | ProceduralMaterialSystem | Runtime procedural material creation |
+| AnimationTreeRegistry | Global named animation tree definitions |
+| AnimationTreeSystem | Runtime evaluation of registry-referenced animation trees |
 
 #### PlayerControllerSystem
 
@@ -276,6 +278,14 @@ One-shot actions (`E`, `F`, `I`, `Escape`) are still matched by `keysym.sym`.
 
 The spawner uses the entity's `TransformComponent` for spawn position/rotation. When the spawner itself moves/rotates/scales in the editor, the spawned character is updated to match; when the spawner is stationary, the character is left alone so it can move on its own. Spawned characters are created without `EditorMarkerComponent` and removed from the editor UI cache so they remain visible but are not selectable/editable in the editor. Registry changes that bump the character version trigger an immediate respawn. Scene serialization stores plain `spawnDistance`/`despawnDistance` values for readability while the component keeps squared values for comparisons.
 
+#### AnimationTreeComponent
+
+- `treeName` - Name of the animation tree in `AnimationTreeRegistry`.
+- `enabled` - Whether the tree is evaluated.
+- `useRootMotion` - Whether root motion from the animation drives the character's linear velocity.
+
+The actual tree definition (node hierarchy, state machines, animations) lives in the `AnimationTreeRegistry`, persisted to `animation_tree.json`.  Trees are authored in the registry editor (**Tools -> Animation Tree Registry**), where each entry can also select a skeleton source from the `Characters` resource group (one representative mesh per skeleton) to populate animation-name dropdowns.  Old scenes and prefabs that stored the tree inline or referenced an `AnimationTreeTemplate` are migrated automatically on load.
+
 ### Physics System
 
 Uses Jolt Physics with custom wrapper (legacy - `src/physics/physics.h`, current - `src/features/editScene/physics/physics.h`):