fix: align maintenance scripts with the published repo layout

[Severn17]

Summary

Align the repository maintenance scripts with the files that actually exist in this package.

Changes

• add a minimal ESLint config for scripts/**/*.js and tests/**/*.mjs
• add a real repository validation script
• point build, lint, and validate at the current repo layout
• remove the missing README.zh-CN.md entry from package.json.files
• replace the broken dev TypeScript watch flow with a maintenance watch loop

Validation

• npm run lint
• npm run build
• npm run validate
• npm test -- --run