fix: use browser-compatible url imports

[HugoHSun]

🧰 Changes

Switches the url imports back to the bare Node module specifier instead of node:url.

The package already relied on consumers polyfilling Node’s url module for browser builds. After the move to tsdown, the published output started preserving node:url, which browser bundlers may not resolve through existing url fallbacks.

This keeps the runtime behavior the same while restoring compatibility for browser-bundled consumers like @readme/oas-to-snippet.