Harden import and paste validation, fix duplicate exports and variable declarations

src/components/PropertiesPanel.tsx

@@ -727,6 +727,12 @@ function PartInspector({ partId }: { partId: string }) {
         />
       </div>
 
+      {part.type === 'pipe' && (
+        <div className="rounded-lg border border-zinc-800 bg-zinc-900/30 p-2.5 text-[11px] leading-snug text-zinc-400 mt-2">
+          <span className="font-semibold text-zinc-300">Tip:</span> Drag the glowing blue ends of the pipe in the 3D view to stretch its length.
+        </div>
+      )}
+
       {part.type === 'pump' && <PumpCard part={part} />}
       {part.type === 'airCompressor' && <AirCompressorCard part={part} />}
       {part.type === 'reservoir' && <ReservoirCard part={part} />}