feat: expose reproducible World Setup seeds

[christopherjnelson]

Summary

• expose editable world, spawn, roster, behavior-assignment, and casual-cleaner seeds in World Setup
• deterministically regenerate generated behavior assignments while preserving explicit manual assignments
• display engine-owned objective-version provenance and rehydrate setup values from authoritative resets

Scope

• World Lab UI and focused behavior tests only
• archive-based setup loading remains a follow-up

Validation

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• pnpm format
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• pnpm build
• pnpm test:e2e