reduceBlob meaning and pinned-directive preservation

reduceBlob must never discard pinned user directives, even under junk classification, tight budgets, low lexical variety, sampling, or overlapping hard windows. During reassembly, preserve a newline between distinct adjacent paragraphs; concatenate without a separator only contiguous hard-window pieces from the same original line. These rules prevent distillation from erasing explicit constraints or changing paragraph meaning.