feat: collect and report 1-min load average

internal/aggregate/window.go

@@ -16,7 +16,9 @@ type Window struct {
 
 	uptime uint64
 
-	// DB metrics — populated only when a DB collector is registered.
+	load float64
+
+	// DB metrics. populated only when a DB collector is registered.
 	hasDB              bool
 	dbDriver           uint8
 	dbConnPctSum       float64
@@ -34,6 +36,7 @@ type Snapshot struct {
 	MemAvg  float64
 	DiskAvg float64
 	Uptime  uint64
+	Load    float64
 
 	// nil when DB monitoring is not enabled.
 	DBDriver         *uint8
@@ -66,6 +69,10 @@ func (w *Window) SetUptime(value uint64) {
 	w.uptime = value
 }
 
+func (w *Window) SetLoad(value float64) {
+	w.load = value
+}
+
 func (w *Window) AddDBConnPct(v float64) {
 	w.dbConnPctSum += v
 	w.dbConnPctCount++
@@ -118,6 +125,7 @@ func (w *Window) Snapshot() Snapshot {
 		MemAvg:    memAvg,
 		DiskAvg:   diskAvg,
 		Uptime:    w.uptime,
+		Load:      w.load,
 	}
 
 	if w.hasDB {