Guard custom stats and word libraries against duplicate registration

[henry3218]

Summary

• ensure the Chevalier stat bootstrapper reuses existing BaseStatAsset entries instead of adding duplicates
• update the Warrior stat initialization to share existing Resist/Dodge/Accuracy assets when they have already been created
• reuse the existing Chinese word library assets when reloading dictionaries so repeated loads do not register duplicates

Testing

• not run (not requested)

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https://chatgpt.com/codex/tasks/task_e_68f86ced85008321bd800778b3a6179a

[henry3218]

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