feat(orchestration): add secondary objective builder

[HelloThisWorld]

Summary

Closes #

Checklist

• pnpm lint, pnpm typecheck, and pnpm test pass locally
• pnpm check:public-contracts passes — or a stable contract changed
  intentionally and the snapshot under contracts/ is updated in
  this PR
• Documentation updated for any user-visible behavior change
• CHANGELOG entry added for any user-visible change (required whenever
  a contract snapshot changed)
• Everything is in English (code, comments, docs, commit messages)
• No employer or client proprietary content — examples and fixtures
  are synthetic
• No credentials, tokens, or secret values anywhere in the diff,
  fixtures, or recorded test output