Agent Skills: implementation-preflight

Use before starting coding implementation, bug fixes, refactors, feature work, test additions, or engineer-agent handoffs where code or dependencies may change. Choose the implementation strategy first: no-op/delete, reuse existing code or workflows, refactor/extend, stdlib/native feature, already-installed dependency, mature new package/plugin, or minimal new code. Requires current web investigation before adopting any new package/plugin and explicit approval for high-impact dependency or plugin changes.