tranche tweak

src/orderbuild.js

@@ -46,7 +46,7 @@ export function timesliceTranches() {
         window = Math.round(duration / n)
     }
     if( window < 60 )
-        window = 60
+        window = 60  // always allow at least one minute for execution
     const amtPerTranche = Math.ceil(MAX_FRACTION / n)
     duration -= 15  // subtract 15 seconds so the last tranche completes before the deadline
     for (let i = 0; i < n; i++) {