pnpm update error output handling

[Phavya-jfrog]

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pnpm install failures previously returned a generic error with no pnpm output in the returned error, making failures hard to diagnose.

This PR tees stdout/stderr in runPnpmInstall() and appends the captured output to the error on failure, while still streaming output live to the terminal.

[reshmifrog]

@Phavya-jfrog please add required labels

[Phavya-jfrog]

@Phavya-jfrog please add required labels

I dont have access to add labels