Add animation blend tree parser, ID and AnimationTree node with runtime updates

[TiernanDeFranco]

Motivation

• Add support for animation blend trees so multiple animation slots can be combined and an output animation can be resolved at runtime.

Description

• Add a simple panim_tree parser and AnimationBlendTreeDef with parse_panimtree in perro_animation to read slot definitions from text sources.
• Introduce AnimationBlendTreeID in perro_ids to identify blend tree resources.
• Implement the AnimationTree node and related types in perro_nodes/src/nodes/animation_tree.rs, including slot management, graph node kinds, evaluation (evaluate_output_animation), slot controls (play_slot, pause_slot, seek_slot, etc.) and weight manipulation (set_blend_weight).
• Register the node in perro_nodes::nodes and node_registry, and add runtime internal update hooks and an internal_update implementation in runtime_project/perro_internal_updates to advance playing slots and record the last resolved output animation.

Testing

• Run unit tests included in panim_tree and animation_tree via cargo test, and the added tests passed.
• Ran workspace tests with cargo test --workspace and they completed successfully.

---

Codex Task