test: add OpenUI CLI helper coverage

[ProfTrader]

Summary

• Add focused Vitest coverage for CLI package-manager detection.
• Add non-interactive argument resolution coverage for provided and missing required args.
• Keep CLI builds clean by excluding test files from the production tsconfig and adding a test-only tsconfig.

Fixes #554

Verification

• pnpm --filter @openuidev/cli run test
• pnpm --filter @openuidev/cli run build:cli
• pnpm exec prettier --check packages/openui-cli/package.json packages/openui-cli/tsconfig.json packages/openui-cli/tsconfig.test.json packages/openui-cli/src/lib/detect-package-manager.test.ts packages/openui-cli/src/lib/resolve-args.test.ts
• pnpm exec eslint src/lib/detect-package-manager.test.ts src/lib/resolve-args.test.ts from packages/openui-cli
• pnpm install --frozen-lockfile --ignore-scripts