fix: the corroboration guard is all-or-nothing, not lockstep

CI failed on this PR: `test_body_map_package_agrees_with_the_witness_map`
required `repos.yaml` to DECLARE `package:` for every witness row that names
one, and tests.yml pins the sibling Mind checkout to `main`, where the field
does not exist yet. The rest of the fix already tolerated that — `canonical_key`
falls back to the hand table, with a test pinning it — but this guard did not,
so the half that was designed to stand alone could not.

Absence of the field is an older body map, not a contradiction: a map declaring
NO package anywhere has nothing to corroborate, and the guard stands down. The
moment it declares even one, every witness row that names a package must have
one — so a PARTIALLY declared map still fails, which is what a new library added
without its `package:` would look like. That is a stronger guard than the one it
replaces, not a weakened one.

Verified against CI's exact condition — this branch's Brain against a PyAutoMind
checkout at origin/main, zero `package:` rows: 515 pass. Against the branch's
Mind, with all seven declared: 515 pass. Mutation: declaring one package and not
the rest fails the guard naming the other six.

Also fixes the DeprecationWarning this PR introduced (`maxsplit` passed
positionally in `unreachable_repos`). The identical warning from
`normalise_repo` is pre-existing and left alone.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Nj7cTnL8Ke5WoNsdGVhCKn

Author: claude

agents/faculties/sizing/_sizing.py

@@ -183,7 +183,7 @@ def unreachable_repos() -> dict:
         name: "name contains a '.' or '/', which normalise_repo truncates — "
               "no @-mention can reach it"
         for name in _body_map_specs()
-        if re.split(r"[./]", name, 1)[0] != name
+        if re.split(r"[./]", name, maxsplit=1)[0] != name
     }
 
 

tests/test_policy_seams.py

@@ -273,11 +273,22 @@ def test_body_map_package_agrees_with_the_witness_map():
     something compares them — #269 verified every witness row by reading each
     repo's own tree, and this pins the body map to that verified evidence rather
     than to a second, unchecked transcription.
+
+    ALL-OR-NOTHING, not lockstep. A body map that declares NO package anywhere
+    simply predates the field (this repo's CI pins the sibling Mind checkout to
+    `main`, and an adopting fork may never adopt it) — absence is an older map,
+    not a contradiction, so there is nothing to compare and the guard stands
+    down. Once the map declares even one, every witness row that names a package
+    must have one: a PARTIALLY declared map is the drift this exists to catch,
+    and is what a new library added without its `package:` would look like.
     """
     sys.path.insert(0, str(BRAIN_HOME / "agents" / "conductors" / "refactor"))
     import _refactor
 
     specs = _sizing._body_map_specs()
+    if not any("package" in spec for spec in specs.values()):
+        return  # a body map from before the field existed — nothing to corroborate
+
     disagree = {}
     for key, witness in _refactor.TEST_WITNESS.items():
         repo, _, test_dir = witness.partition("/")