feat: complete guided research presentation flow

[Mike-Zhuang]

Summary

• make every prepared guided stage expose a distinct selectable English/Chinese response
• align the frozen Event Pack and claim review with the gold safe-haven versus liquidity-stress presentation story
• show stored natural-language evidence flowing into validated structured cognition decisions during run playback
• generate, validate, persist, and automatically restore one grounded English interpretation for the completed experiment
• preserve human review boundaries and reject rule-fallback artifacts from the prepared hybrid path

Validation

• backend: full pytest suite
• backend: full Ruff check
• frontend: 291 tests
• frontend: TypeScript typecheck and production build
• exact CPython 3.12.13 environment

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