V2: `pnpm install` fails when `pnpm-lock.yaml` is not present

[robbear]

On a fresh clone of branch a0e5847, if I remove pnpm-lock.yaml so as to regenerate it and run pnpm install, the installation fails.

[NEXTRA-ESM] DTS Build start
│ [NEXTRA-TYPES] DTS Build start
│ src/plugin.ts(173,43): error TS2345: Argument of type 'string | undefined' is no
│   Type 'undefined' is not assignable to type 'string'.
│ Error: error occured in dts build

The committed lock file allows a successful pnpm install, but apparently can't be regenerated. This blocks my project from creating its own variant of the lock file.

[robbear]

Confirmed the same on the latest core.