running tsup with --watch, can't kill it with CTRL + C

I have a simple package, it looks like this:

```
{
"name": "some-project",
"version": "1.0.0",
"type": "module",
"main": "./dist/index.js",
"types": "./dist/index.d.ts",
"scripts": {
"build": "tsup src/index.ts src/urbit/* --format esm --minify --dts --out-dir dist",
"dev": "npm run build -- --watch"
},
"dependencies": {},
"devDependencies": {
"tsup": "^8.0.1",
}
}
```

If I run `npm run dev`, I can't kill the process with SIGINT (CTRL + C), I have to SIGTERM it manually.

I'm running it within tmux on macOS Ventura.

Any idea as to what's going on? Is this a bug?

Start by reproducing the npm run dev command, which invokes tsup with --watch, inside tmux on macOS Ventura. Investigate how the watch process handles SIGINT from Ctrl+C and confirm the behavior outside tmux as a comparison. Done means Ctrl+C exits the watch process cleanly without requiring SIGTERM.

Written by the indexing model from the issue text.