perr() in parse.ww wrote the "w6a: " prefix with a hand-counted length
of 4, but the string is 5 bytes — the trailing space was dropped, so
every assembler diagnostic printed as "w6a:<file>" with no separating
space. Replace the prefix length (and the ": " / "\n" literal writes in
the same function) with the string's own .len via the local-binding
idiom, fixing the off-by-one and closing the hand-count class here. Uses
str-variable .len (correct on both stages), not "literal".len (cstage
miscompile, #14), so this is byte-identical cs==ww.
Verified: w6a_ww on a bad input now writes "w6a: <file>: <msg>\n" with
the space restored; w6c and w6c_ww emit byte-identical asm for the
regenerated main.combined.ww.
Hojun-Cho
dbb52e25fe