fix: make TypeScript 6 bump CI-compatible

[vitormattos]

Summary

• bump TypeScript to 6.0.2
• remove deprecated tsconfig option that fails under TS6
• add type declaration for vite/modulepreload-polyfill side-effect import
• keep OpenAPI generation working via npx without incompatible peer dependency install

Validation

• npm run ts:check
• npm run test
• npm run typescript:generate
• git status --porcelain openapi*.json src/types/openapi/openapi*.ts (no diff)

This should unblock the dependency bump scenario covered in #46.