The last flip casualty in the test-migration class (the filed #66
"WW_W6C under sep" framing was a phantom — cstage honors the override;
see re-scoped #66 for the real wwstage align-up). 809_idx_structlit_store's
asm_byte_identical drove `bin/ww build` then read <src>.s next-to-source;
the flip relocates asm to .sepwork/, so it now drives `ww build --sep -o
<stem>` (cstage + WW_W6C=w6c_ww wwstage legs) and byte-diffs the
concatenated per-package .sepwork/*.s. callee_capture imports strings, so
concat-all is the faithful equivalent of the old whole-program compare.
Adding --sep is flip-invariant (green pre- and post-flip). 809_delete_range
is flip-invariant (direct w6c -o), left untouched. Test-only; all 5 pins HOLD.