Stage multi-step Go edits so each compile error stays meaningful

When you add a feature to Go code in steps that won't compile until the last one, add each import in the step that first uses it, not up front. An imported package that nothing uses is a compile error in Go, so adding imports early buries the expected 'undefined: X' errors for functions not written yet under extra 'imported and not used' noise. Constants and helper functions that nothing uses yet are fine, because Go does not reject those. When the work is split across steps, report the expected remaining error after each step, so nobody mistakes it for a regression.