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Fold blanktag's three blank-emitting loops into one The filter-out-BOS/EOS-then-emit sequence was written out three times, so teaching it about StreamCmd meant editing all three — and each ended in a `_ => {}` that would have silently dropped anything they missed. emit_blanks matches Block exhaustively instead, so the next variant is one compile error rather than three dropped blocks. The marker strings were also spelled out in all three filters on top of the two consts; they are now consts used as patterns.