Passing buf[1:] of a [MAX]u8 as a call arg dropped the default-hi
length (the arg-push N_SLICE arms' fallback covered only named-alias
bases). Same type-table resolve at pushargsrev local+global. This
closes the def-dim dimension family by construction: every N_INTLIT-
keyed dim consumer (cgslice, cgdot, letemitsize, arg-push) now
carries the tichase().alen fallback — grep-proven, no consumer
remains. Fourth member surfaced by the family grep.
