fix: consistent hasMore pattern and remove double-counted LoadCount in scoring

- Adopt vacuum_handler's hasMore pattern: over-fetch by 1, check
  len > maxResults, and truncate — consistent truncation semantics
- Remove direct LoadCount penalty in calculateBalanceScore since
  LoadCount is already factored into effectiveVolumeCount for
  utilization scoring; bump utilization weight from 40 to 50 to
  compensate for the removed 10-point load penalty

weed/plugin/worker/volume_balance_handler.go

@@ -228,7 +228,7 @@ func (h *VolumeBalanceHandler) Detect(
 	if maxResults <= 0 {
 		maxResults = 1
 	}
-	results, err := balancetask.Detection(metrics, clusterInfo, workerConfig.TaskConfig, maxResults)
+	results, err := balancetask.Detection(metrics, clusterInfo, workerConfig.TaskConfig, maxResults+1)
 	if err != nil {
 		return err
 	}
@@ -236,7 +236,11 @@ func (h *VolumeBalanceHandler) Detect(
 		glog.Warningf("Plugin worker failed to emit volume_balance detection trace: %v", traceErr)
 	}
 
-	hasMore := len(results) >= maxResults
+	hasMore := false
+	if maxResults > 0 && len(results) > maxResults {
+		hasMore = true
+		results = results[:maxResults]
+	}
 
 	proposals := make([]*plugin_pb.JobProposal, 0, len(results))
 	for _, result := range results {

weed/worker/tasks/balance/detection.go

@@ -370,11 +370,13 @@ func calculateBalanceScore(disk *topology.DiskInfo, sourceRack, sourceDC string,
 
 	score := 0.0
 
-	// Prefer disks with lower effective volume count (current + pending moves)
+	// Prefer disks with lower effective volume count (current + pending moves).
+	// LoadCount is included so that disks already targeted by planned moves
+	// appear more utilized, naturally spreading work across targets.
 	if disk.DiskInfo.MaxVolumeCount > 0 {
 		effectiveVolumeCount := float64(disk.DiskInfo.VolumeCount) + float64(disk.LoadCount)
 		utilization := effectiveVolumeCount / float64(disk.DiskInfo.MaxVolumeCount)
-		score += (1.0 - utilization) * 40.0 // Up to 40 points for low utilization
+		score += (1.0 - utilization) * 50.0 // Up to 50 points for low utilization
 	}
 
 	// Prefer different racks for better distribution
@@ -387,8 +389,5 @@ func calculateBalanceScore(disk *topology.DiskInfo, sourceRack, sourceDC string,
 		score += 20.0
 	}
 
-	// Prefer disks with lower current load
-	score += (10.0 - float64(disk.LoadCount)) // Up to 10 points for low load
-
 	return score
 }