fix: Remove duplicate portrait-image and unify sprite display to #portrait container only

[oco777]

Summary

• remove the lingering portrait-image element attached directly to the actor root before applying sprites
• clear and rebuild the portrait container so it always hosts a single Image element for sprite display
• rely solely on Sprite assignments from actor data and drop backgroundImage/Texture2D usage

Testing

• not run (not supported in this environment)

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Codex Task