terminal: preserve quickstart errors and detect interrupts robustly

[lofimichael]

Summary

stripe terminal quickstart was comparing prompt interrupts by string and rewrapping errors into identical strings before returning them.

This updates the quickstart path to use errors.Is(err, promptui.ErrInterrupt) and return the original errors directly. That keeps interrupt handling robust if those errors are wrapped, without changing the existing behavior for non-interrupt failures.

Testing

• make lint
• make ci

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[tomer-stripe]

hi! i'm kind of curious, are you using this feature? we've been trying to find users of it to learn more about they're usage