“For all their freeform noise, Cate Le Bon’s songs have pure hearts. Neither the rock canon nor concrete villains exist in the Welsh punk’s charming, surrealist world, which she assembles by scrambling signifiers and imbuing them with more emotion than most deconstructionists ever manage. Halfway through “Rock Pool,” from a new EP collecting off-cuts from this year’s sublime Crab Day, she poses a q”