Convert an internal package to TypeScript

Modernize an internal package without mixing mechanical moves with semantic changes or obscuring file history. Treat packages/README.md as the authority for the package's lifetime architecture; this skill owns only the conversion workflow.

Confirm this workflow applies

Read packages/README.md completely, then inspect the package, its consumers, and comparable current packages. Confirm that the package is internal-only and can adopt the documented single-build TypeScript and ESM contract.

Before editing: