fix(mqtt): resolve B-9 by implementing lazy get_logs_dir() evaluation

- Replace import-time LOGS_DIR cwd binding with dynamic get_logs_dir() function
- Implement PEP 562 __getattr__ and __dir__ for transparent LOGS_DIR backward compatibility
- Update audit-log callers in mqtt_common.py and registry.py to use dynamic resolution
- Add 5 regression guards in tests/test_tier1_unit.py (276/276 PASS)
- Update IMPROVEMENTS.md, VERSIONS.md, registry.md, and include plan and peer review reports

tests/test_tier1_unit.py

@@ -402,3 +402,74 @@ def test_b10_find_workspace_uuid_runs_without_pyyaml(tmp_path):
     assert r.returncode == 0, f"resolution path still needs PyYAML: {r.stderr}"
     assert "yaml" not in r.stderr.lower(), f"PyYAML touched at runtime: {r.stderr}"
 
+
+# ===========================================================================
+# B-9: LOGS_DIR import-time cwd binding resolution regression guards
+# ===========================================================================
+
+def test_b9_logs_dir_follows_cwd_changes(mam_sandbox, tmp_path, monkeypatch):
+    """B-9: the audit-log root must be resolved per call, not frozen at import."""
+    mq = get_mqtt_common(mam_sandbox)
+    monkeypatch.delenv("DELEGATE_JOB_LOGS_DIR", raising=False)
+    a = tmp_path / "a"; b = tmp_path / "b"
+    a.mkdir(); b.mkdir()
+
+    # realpath on both sides: pytest's tmp_path happens to be pre-resolved today,
+    # but relying on that is an undocumented dependency (C1').
+    def logs_under(p):
+        return os.path.realpath(os.path.join(str(p), ".mam", "delegate_job_logs"))
+
+    monkeypatch.chdir(a)
+    assert os.path.realpath(mq.get_logs_dir()) == logs_under(a)
+    monkeypatch.chdir(b)
+    assert os.path.realpath(mq.get_logs_dir()) == logs_under(b)
+    # the compat alias must follow too (T1: a surviving global fails here)
+    assert os.path.realpath(mq.LOGS_DIR) == logs_under(b)
+
+
+def test_b9_audit_log_lands_under_the_current_cwd(mam_sandbox, tmp_path, monkeypatch):
+    """B-9/T3: assert the FILE appears — a swallowed NameError must not pass."""
+    mq = get_mqtt_common(mam_sandbox)
+    monkeypatch.delenv("DELEGATE_JOB_LOGS_DIR", raising=False)
+    monkeypatch.chdir(tmp_path)
+    mq.init_job_log("b9job", {"status": "pending"})
+    assert (tmp_path / ".mam" / "delegate_job_logs" / "b9job" / "meta.json").exists(), \
+        "audit log did not land under the current cwd (the best-effort handler may have swallowed an error)"
+
+
+def test_b9_logs_dir_env_override_is_dynamic(mam_sandbox, tmp_path, monkeypatch):
+    """B-9: DELEGATE_JOB_LOGS_DIR must be honoured at call time, both ways."""
+    mq = get_mqtt_common(mam_sandbox)
+    monkeypatch.chdir(tmp_path)
+    monkeypatch.setenv("DELEGATE_JOB_LOGS_DIR", "/tmp/b9-override")
+    assert mq.get_logs_dir() == "/tmp/b9-override"
+    monkeypatch.delenv("DELEGATE_JOB_LOGS_DIR")
+    # equality, not inequality — clearing the env must restore the cwd default (Rev.2 §3)
+    assert os.path.realpath(mq.get_logs_dir()) == \
+        os.path.realpath(os.path.join(str(tmp_path), ".mam", "delegate_job_logs"))
+
+
+def test_b9_no_module_level_logs_dir_binding():
+    """B-9/T1: a surviving module global would make __getattr__ dead code."""
+    import ast, pathlib
+    src = (pathlib.Path(__file__).resolve().parent.parent / ".agents" / "skills"
+           / "multi-agent-mux-delegate-job" / "scripts" / "mqtt_common.py")
+    tree = ast.parse(src.read_text())
+    for node in tree.body:                      # module scope only
+        if isinstance(node, ast.Assign):
+            for t in node.targets:
+                assert not (isinstance(t, ast.Name) and t.id == "LOGS_DIR"), \
+                    f"line {node.lineno}: module-level LOGS_DIR binding shadows __getattr__ (B-9/T1)"
+        elif isinstance(node, ast.AnnAssign):   # C2-b: LOGS_DIR: str = ... parses as AnnAssign
+            assert not (isinstance(node.target, ast.Name) and node.target.id == "LOGS_DIR"), \
+                f"line {node.lineno}: annotated module-level LOGS_DIR binding shadows __getattr__ (B-9/T1)"
+
+
+def test_b9_logs_dir_stays_discoverable(mam_sandbox):
+    """B-9/C2-a: PEP 562 __dir__ keeps LOGS_DIR visible to dir() and tooling."""
+    mq = get_mqtt_common(mam_sandbox)
+    assert "LOGS_DIR" in dir(mq)
+    assert hasattr(mq, "LOGS_DIR")              # true via __getattr__ even without __dir__
+    assert dir(mq).count("LOGS_DIR") == 1       # set-based __dir__ must not duplicate
+
+