Copying AnimationLibrary resources(make unique), but no deep duplicate it's sub animation resources.

Tested versions

• Reproducible in: 4.5stable, 4.4.1stable

System information

Godot v4.5.stable - Windows 10 (build 19045) - Multi-window, 1 monitor - Vulkan (Mobile) - dedicated NVIDIA GeForce RTX 4070 (NVIDIA; 32.0.15.7628) - 12th Gen Intel(R) Core(TM) i5-12490F (12 threads) - 31.81 GiB memory

Issue description

When I try to copy AnimationLibrary resources with using make unique, modifying animation resources still affects the original copy. After a long period of trying😅, I found that the correct behavior can only be obtained by enabling make unique for the sub animation resources in the AnimationEditor. This should indicate that when make unique is enabled for animation library resources by default, but not recursive to sub animation resources. I think is a issue because when we want to copy(duplicate_deep) AnimationLibrary resources(make unique), the objects we want to modify are sub animation resources, so we should default to enabling make unique recursion or add another option 'make unique(recursive)'. Maybe related to #100673.

Demo:

https://github.com/user-attachments/assets/39603012-4396-445f-9c5f-65b4ebd24bec

Steps to reproduce

1. Copy a AnimationLibrary resource from one to another AnimationPlayer
2. Make it unique
3. Tweak a animation e.g named 'idle' in AnimationLibrary
4. You will find that the original copy be modified at the same time
5. Open 'manage animations' option in the AnimationEditor, make 'idle' sub animation resource unique and then tweak it
6. Check the original copy not modified

Minimal reproduction project (MRP)

anim_2025-10-02_02-56-15.zip

Start with the attached minimal reproduction project and reproduce the resource-copying steps in the AnimationEditor, focusing on AnimationLibrary and its sub-animation resources. Compare the behavior before and after making the idle animation unique; done means editing the copied animation no longer changes the original, with the intended recursive behavior or option confirmed by the maintainer.