extend-not-duplicatelisted

# Extend existing scripts; don't duplicate them If you're about to write a new script that's >80% the same as an existing one with small differences (different env, different mode, different flag combo), extend the existing one with a CLI argument or config option instead of writing a parallel copy. ## Why Two near-identical scripts diverge over time. A bug fix lands in one and not the other. A new feature gets added inconsistently. Reviewers can't tell which is canonical. The duplicated logic compounds with every change. ## How to apply When you notice you'd be copying an existing script and changing a few values: - Identify what's actually different — usually a flag, env var, or config field. - Add that as a CLI arg (`--mode prod` / `--target dev`) or env knob to the existing script. - Update callers if needed. If the differences are structural (different control flow, different inputs, different outputs), then a separate script IS appropriate — but check first whether the structural difference can be expressed as a parameter.