BLAME-006a: blame skips a deleted file instead of folding an empty layer (root mis-attribution)

be blame: attributes lines to the ROOT commit for a file that was DELETED then RE-ADDED, because the blame weave SKIPS the delete instead of folding an empty (delete) layer — so the old tokens never die and the readd's structurally-equal tokens (titles, blank lines) inherit the root commit's seq. Split from BLAME-006 (the correctness half). Method: Issues.

Input

Context

Repro: be blame:ABC.md pins 5 pieces to ?c7184818#initial (root). ABC.md was a DIFFERENT doc at root, DELETED at 006b9039 (18Nov24 reorg), RE-ADDED as the current doc at 8948262e (22May, its true add commit, owns 20/28). The 5 root-pinned pieces are line-1 H1 + 4 blank lines before ## headers — content-only RAPHash (BLAME/WEAVE.c:502,510) COLLIDES across the delete/readd.
Root cause: graf/BLAME.c:480 (if (dr==BLAME_DESC_ABSENT) continue;) + twin :492 — when the path is absent at a commit, GRAFFileWeave SKIPS it instead of folding an empty layer, so old tokens stay alive; the readd content folds and the WEAVE EQ keep-seq branch (WEAVE.c:579-586) matches new title/blank tokens to the still-alive root tokens → they inherit root's seq.

Goals

A delete is folded as an explicit empty (all-delete) layer so tokens DIE at the delete commit → a readd is a clean all-INS at the readd commit; no root leak.
be blame:ABC.md attributes all pieces to 8948262e+ (or their real authors), none to root.

Constraints

Behaviour-preserving for files that were never deleted: GRAFblameident / GRAFblameruns byte-identical. graf change gates for review.

WIP

Design decisions

Reuse the existing all-delete path (WEAVE.c:534-540, nlen==0): at BLAME.c:480/492, on BLAME_DESC_ABSENT, fold an EMPTY version (all tokens deleted) rather than continue.

TODOs

Repro-first: a hermetic delete-then-readd file; assert blame attributes the readd commit, not root (RED pre-fix). → graf/test/blame-readd.sh.
Fix the skip-on-absent to fold an empty layer.
ctest green incl. GRAFblameident (unaffected attributions byte-identical).
Gate + land.

Blockers and bummers

Pairs with BLAME-006b (the perf half) — independent; land separately.

Outcome

FIX-READY ($HOME/todo/BLAME-006a, stopped at commit boundary). Both absent points in graf/BLAME.c::GRAFFileWeave (~:483-528, :569): on BLAME_DESC_ABSENT/fetch-miss, if the file was alive in the last folded layer (have_prev), set is_delete + reset *cur_blob to empty instead of skipping; the empty blob flows through WEAVEFromBlob → empty wnu → the existing nlen==0 all-delete path (WEAVE.c:564-570), so live tokens die at the delete and the readd is a clean all-INS. Guards: skip delete-on-empty; reset prev_n=0 after a delete (early-stop can't false-match a stale chain); still skips when the file was never present. Both descent paths (index-served + GRAF_BLAME_NOINDEX keeper-inflate) give identical correct output. New graf/test/blame-readd.sh (GRAFblamereadd, table-driven top-level + subdir, RED→GREEN). Full ctest 300/300 (+1), GRAFblameident byte-identical. Awaiting gate to land.