When pnpm is installed as a standalone executable in environments without
a system Node.js (e.g. Docker containers), the `@pnpm/exe` preinstall
script (`node setup.js`) fails because `node` is not on PATH. This broke
version switching via the `packageManager` field in package.json since
v10.30.2, which changed `getCurrentPackageName()` to return `@pnpm/exe`
instead of platform-specific package names like `@pnpm/linux-x64`.
Install with `--ignore-scripts` and link the platform-specific binary
in-process instead. The setup logic is inlined because setup.js can't
be loaded at runtime: `require()` fails on ESM (pnpm v11+) and
`import()` is intercepted by pkg's virtual filesystem in standalone
executables.
Closes#10687
