fix: collect topology once and track capacity changes locally

Remove the topology refresh within the loop as it gives a false sense
of correctness - the refreshed topology could still be stale (minutes old).

Instead, we:
1. Collect topology once at the start
2. Track capacity changes ourselves via freeEcSlot decrement after each move

This is more accurate because we know exactly what moves we've made,
rather than relying on potentially stale topology refreshes.

weed/shell/command_volume_server_evacuate.go

@@ -157,6 +157,9 @@ func (c *commandVolumeServerEvacuate) evacuateNormalVolumes(commandEnv *CommandE
 
 func (c *commandVolumeServerEvacuate) evacuateEcVolumes(commandEnv *CommandEnv, volumeServer string, skipNonMoveable, applyChange bool, writer io.Writer) error {
 	// find this ec volume server
+	// We collect topology once at the start and track capacity changes ourselves
+	// (via freeEcSlot decrement after each move) rather than repeatedly refreshing,
+	// which would give a false sense of correctness since topology could be stale.
 	ecNodes, _ := collectEcVolumeServersByDc(c.topologyInfo, "")
 	thisNodes, otherNodes := c.ecNodesOtherThan(ecNodes, volumeServer)
 	if len(thisNodes) == 0 {
@@ -167,20 +170,6 @@ func (c *commandVolumeServerEvacuate) evacuateEcVolumes(commandEnv *CommandEnv,
 	for _, thisNode := range thisNodes {
 		for _, diskInfo := range thisNode.info.DiskInfos {
 			for _, ecShardInfo := range diskInfo.EcShardInfos {
-				// Refresh topology to get updated free slot counts before moving each EC volume
-				if applyChange {
-					if topologyInfo, _, err := collectTopologyInfo(commandEnv, 0); err != nil {
-						fmt.Fprintf(writer, "update topologyInfo for EC: %v\n", err)
-					} else {
-						ecNodesNew, _ := collectEcVolumeServersByDc(topologyInfo, "")
-						_, otherNodesNew := c.ecNodesOtherThan(ecNodesNew, volumeServer)
-						if len(otherNodesNew) > 0 {
-							otherNodes = otherNodesNew
-							c.topologyInfo = topologyInfo
-						}
-					}
-				}
-
 				hasMoved, err := c.moveAwayOneEcVolume(commandEnv, ecShardInfo, thisNode, otherNodes, applyChange, writer)
 				if err != nil {
 					fmt.Fprintf(writer, "move away volume %d from %s: %v\n", ecShardInfo.Id, volumeServer, err)