Fix duplicate ACP model selector options

[Yuqing (mydmdm)]

Summary

• deduplicate ACP select options by exact control value in the shared canonical projection
• preserve first-published metadata and retain equal labels with distinct values
• document the selector normalization contract and cover the Copilot CLI 1.0.89 response shape

Fixes #250

Validation

• pnpm --filter @huabu/shared test (53 files, 655 tests)
• pnpm typecheck
• pnpm format
• pnpm lint:fix