test(issue-57): the audit log follows a moved registry

New file tests/test_issue57_logs_follow_registry.py: the resolver (L1),
registry.py (L2), the wrapper's submit/wait/logs (L3), publish_event.py
(L4), control_plane.from_env, worktree_prepare, status.sh, the comment-5
disk fallback, and the invariant that an explicit DELEGATE_JOB_LOGS_DIR
still wins. Every test ends by asserting the workspace's own
.mam/delegate_job_logs was never created.

Two existing tests gain monkeypatch.delenv("MAM_JOBS_DIR"): conftest's
autouse _isolate_mam_state_dirs gives every test a MAM_JOBS_DIR, and under
the sibling rule the WORKSPACE_ROOT/cwd fallbacks they assert would
otherwise resolve next to that registry. The order they assert (explicit
root, workspace, cwd) is unchanged.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

tests/test_tier1_unit.py

@@ -495,6 +495,9 @@ def test_b9_logs_dir_follows_cwd_changes(mam_sandbox, tmp_path, monkeypatch):
     monkeypatch.delenv("DELEGATE_JOB_LOGS_DIR", raising=False)
     # Issue #15: with WORKSPACE_ROOT set the root is anchored on the workspace
     # instead; the cwd only decides when neither override is present.
+    # Issue #57: the audit log follows the registry, so the sandbox's
+    # MAM_JOBS_DIR must go too for the cwd to decide.
+    monkeypatch.delenv("MAM_JOBS_DIR", raising=False)
     monkeypatch.delenv("WORKSPACE_ROOT", raising=False)
     a = tmp_path / "a"; b = tmp_path / "b"
     a.mkdir(); b.mkdir()