feat(i18n): support bilingual CLI help and quick start

[XXPermanentXX]

Summary

• add config-based en-US / zh-CN language selection with lightweight colocated LocalizedText
• localize root, group, and command Help, including flags, notes, and natural-language examples
• adapt Quick Start ordering/emphasis and Config UI content to the selected language
• keep generated Skill references in English and remove the unused i18next dependency
• localize Help metadata for commands introduced by the latest main changes and document bilingual Help as a maintenance requirement

Verification

• vp check — 0 errors (5 existing warnings)
• vp run -r build
• vp test packages/runtime/tests/i18n.test.ts packages/commands/tests/config-ui.test.ts packages/commands/tests/e2e/usage-free.e2e.test.ts — 19 passed, 15 skipped
• manual Chinese and English pnpm bl ... --help smoke checks