fix(agent): use nvme_total_capacity fallback for NVMe disk size (#1899)

Some enterprise NVMe drives (e.g. Dell Ent NVMe CM7 U.2) report capacity
via nvme_total_capacity instead of user_capacity.bytes in smartctl output.
The NVMe SMART parser now falls back to nvme_total_capacity when
user_capacity.bytes is zero.

agent/smart.go

@@ -1118,6 +1118,9 @@ func (sm *SmartManager) parseSmartForNvme(output []byte) (bool, int) {
 	smartData.SerialNumber = data.SerialNumber
 	smartData.FirmwareVersion = data.FirmwareVersion
 	smartData.Capacity = data.UserCapacity.Bytes
+	if smartData.Capacity == 0 {
+		smartData.Capacity = data.NVMeTotalCapacity
+	}
 	if smartData.Capacity == 0 && (runtime.GOOS == "darwin" || sm.darwinNvmeProvider != nil) {
 		smartData.Capacity = sm.lookupDarwinNvmeCapacity(data.SerialNumber)
 	}