Refine animation handling and refresh VT baselines

[han4wluc]

Summary

• remove legacy animation authoring and resource compatibility paths so animations only use animations.resourceId and resource types update or transition
• resolve background animation-only actions against persisted presentation state, keep the background update-enter fallback, and refresh the animation docs
• add schema and render-state coverage for the animation cleanup, accept the expected background VT changes, baseline the missing choice/nextLineConfig VT captures, and bump the package version to 0.7.5

Testing

• npx vitest run spec/projectDataSchema.test.js
• npx vitest run puty.spec.js --testNamePattern "addBackgroundOrCg|addLayeredViews|constructPresentationState|addCharacters|addVisuals"
• bun run vt:report