fix: nil-guard clusterInfo, uncap legacy DetectionFunc, deterministic disk type order

- Add early nil guard for clusterInfo in Detection to prevent panics
  in downstream helpers (detectForDiskType, createBalanceTask)
- Change register.go DetectionFunc wrapper from maxResults=1 to 0
  (no cap) so the legacy code path returns all detected tasks
- Sort disk type keys before iteration so results are deterministic
  when maxResults spans multiple disk types (HDD/SSD)

weed/worker/tasks/balance/detection.go

@@ -3,6 +3,7 @@ package balance
 import (
 	"fmt"
 	"math"
+	"sort"
 	"time"
 
 	"github.com/seaweedfs/seaweedfs/weed/admin/topology"
@@ -20,6 +21,9 @@ func Detection(metrics []*types.VolumeHealthMetrics, clusterInfo *types.ClusterI
 	if !config.IsEnabled() {
 		return nil, nil
 	}
+	if clusterInfo == nil {
+		return nil, nil
+	}
 
 	balanceConfig := config.(*Config)
 
@@ -33,14 +37,22 @@ func Detection(metrics []*types.VolumeHealthMetrics, clusterInfo *types.ClusterI
 		volumesByDiskType[metric.DiskType] = append(volumesByDiskType[metric.DiskType], metric)
 	}
 
+	// Sort disk types for deterministic iteration order when maxResults
+	// spans multiple disk types.
+	diskTypes := make([]string, 0, len(volumesByDiskType))
+	for dt := range volumesByDiskType {
+		diskTypes = append(diskTypes, dt)
+	}
+	sort.Strings(diskTypes)
+
 	var allParams []*types.TaskDetectionResult
 
-	for diskType, diskMetrics := range volumesByDiskType {
+	for _, diskType := range diskTypes {
 		remaining := maxResults - len(allParams)
 		if remaining <= 0 {
 			break
 		}
-		tasks := detectForDiskType(diskType, diskMetrics, balanceConfig, clusterInfo, remaining)
+		tasks := detectForDiskType(diskType, volumesByDiskType[diskType], balanceConfig, clusterInfo, remaining)
 		allParams = append(allParams, tasks...)
 	}
 

weed/worker/tasks/balance/register.go

@@ -59,7 +59,7 @@ func RegisterBalanceTask() {
 			), nil
 		},
 		DetectionFunc: func(metrics []*types.VolumeHealthMetrics, info *types.ClusterInfo, config base.TaskConfig) ([]*types.TaskDetectionResult, error) {
-			return Detection(metrics, info, config, 1)
+			return Detection(metrics, info, config, 0)
 		},
 		ScanInterval:   30 * time.Minute,
 		SchedulingFunc: Scheduling,