codemap 0.0.22 — pack measured against git history, and walking both ways

R1-C65 — pack said nothing about what it did with the seed. An unknown name, a
.md path or an attribute id returned the global pack byte for byte, exit 0, under
a header naming the seed. Now every pack carries seeds, unreachable_from_seeds
and coverage, and a seed set that resolves to nothing is a refusal (exit 1).

R1-C66 — a seeded pack walks both ways by default. Against git history (seed the
pack with a changed file on the parent's graph, count the co-changed files in its
first ten) the one-way pack found 18.9 % on 108 commits of bquant, below grep by
names, and 0 % of co-changed tests. Under rules committed before the run, the
two-way walk found 41.6 % there and 59.9 % on 83 held-out commits of codemap.
`--direction uses` keeps the old walk. The agent A/B stays closed: against grep
the interval includes zero on one repository.

Also: R1-C59 (fewer edges on the same input is named by diff and build -o),
R1-C60 (dead-code declares nested definitions it cannot judge), R1-C64
(codemap doctor: does each dependency answer a known question correctly).

Schema 0.13 (unchanged, eleventh release). ANSWER_FORMAT 1 -> 2, only pack
changed shape; every other answer changes by its trailer alone.

Verified from PyPI against 0.0.21 on a tree carrying each defect, PYTHONHASHSEED=7:

  pack --seed seed           0.0.21: caller rank 0.0 (filler), no walk named
                             0.0.22: caller rank 0.117, tests reached, walk: both
  pack --seed no_such        0.0.21: exit 0, global pack  ->  0.0.22: exit 1, refused
  doctor                     0.0.21: no such command  ->  0.0.22: exit 0, both OK
  diff, 7 of 38 calls cut    0.0.21: silent  ->  0.0.22: calls 38 -> 31 named
  graph                      nodes and edges hash identical, 0.13 -> 0.13
  bquant live tree, check    one line: answer format 1 -> 2; exit 0 -> 0