all: mechanical lint fixes

hscontrol/debug.go — pre-size nodes []nodeStatus to len(debugInfo)
    so the loop does not grow under append.
  hscontrol/mapper/batcher_test.go — testing.TB parameter on
    setupBatcherWithTestData renamed t → tb so thelper sees the
    expected name.
  hscontrol/db/text_serialiser.go — reflect.Ptr → reflect.Pointer
    (deprecated alias).