fix(delegation): the path rules live in a stdlib-only module; the package imports without paho (Issue #57, Mac F1)

control_plane and status.sh imported sibling_logs_dir from mqtt_common,
which imports paho at module level, so create/resume's binding and status
died on an interpreter without paho-mqtt (_delegate_py_bin's last fallback
is the PATH's python3). The registry/audit-log path rules move to
lib_py/delegation/logroot.py (standard library only) and mqtt_common
re-exports them. The package's own import chain also reached paho through
service -> publish_event -> publisher, so mqtt_common and publisher import
paho tolerantly and make_client() refuses with a clear error when a broker
is actually needed. control_plane, status.sh, lib.sh's delegate_publish_cmd
and delegate_logs_dir, and the wrapper's _logs_dir_abs import from logroot.

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

.agents/skills/lib_py/delegation/mqtt_common.py

@@ -30,9 +30,14 @@ from dataclasses import asdict, dataclass
 from pathlib import Path
 from typing import Any, Callable, Dict, Iterable, List, Optional
 
-import paho.mqtt.client as mqtt
+try:
+    import paho.mqtt.client as mqtt
+except ImportError:  # the registry and the path rules work without a broker library (Issue #57)
+    mqtt = None      # make_client() says so when a broker is actually needed
 
 from lib_py.delegation import envfile
+from lib_py.delegation.logroot import (  # noqa: F401  (re-exported: this module is the documented home)
+    DEFAULT_REGISTRY_DIR, _workspace_mam_dir, default_registry_dir, get_logs_dir, sibling_logs_dir)
 
 logger = logging.getLogger("delegate_job.mqtt_common")
 
@@ -145,35 +150,10 @@ def load_env_or_report() -> bool:
 # Constants
 # --------------------------------------------------------------------------
 SCHEMA_VERSION = 1
-DEFAULT_REGISTRY_DIR = ".mam/jobs"
 DEFAULT_TOPIC_ROOT = "python/mqtt/jobs"
 LOCK_FILENAME = ".lock"
 
 
-def _workspace_mam_dir(leaf: str) -> Optional[str]:
-    """`$WORKSPACE_ROOT/.mam/<leaf>` when lib.sh has told us which workspace we
-    serve; None otherwise."""
-    root = os.environ.get("WORKSPACE_ROOT")
-    if root and root.strip() and os.path.isdir(root):
-        return os.path.join(root, ".mam", leaf)
-    return None
-
-
-def default_registry_dir() -> str:
-    """Registry root, resolved at call time (Issue #15).
-
-    ``MAM_JOBS_DIR`` wins; otherwise the workspace lib.sh exported as
-    ``WORKSPACE_ROOT``; otherwise the historical cwd-relative ``.mam/jobs``.
-    Anchoring on the workspace is what keeps a test sandbox (or any caller
-    whose cwd is not the workspace) from registering jobs into whichever
-    ``.mam/jobs`` happens to sit under the current directory - the pytest
-    suite used to leave hundreds of onboarding records in the real registry.
-    """
-    env = os.environ.get("MAM_JOBS_DIR")
-    if env and env.strip():
-        return env
-    return _workspace_mam_dir("jobs") or DEFAULT_REGISTRY_DIR
-
 # Persistent audit-log layout: .mam/delegate_job_logs/<job_id>/{meta,events,status}.
 # This is a *separate* artifact from the registry: the registry is the live job
 # record (mutated in place), the audit log is an append-only history that
@@ -183,31 +163,6 @@ EVENTS_FILENAME = "events.ndjson"
 STATUS_FILENAME = "status.json"
 
 
-def sibling_logs_dir(registry_dir: str) -> str:
-    """The audit-log root that pairs with ``registry_dir``: its sibling
-    ``delegate_job_logs``. Pure; reads no environment. Issue #57."""
-    return os.path.join(os.path.dirname(os.path.abspath(registry_dir)), "delegate_job_logs")
-
-
-def get_logs_dir(registry_dir: Optional[str] = None) -> str:
-    """Audit-log root, resolved at call time (B-9).
-
-    ``DELEGATE_JOB_LOGS_DIR`` when set: it means the audit log was moved to a
-    place that cannot be derived from the registry. Otherwise the audit log
-    follows the registry (Issue #57): the ``delegate_job_logs`` next to
-    ``registry_dir``, or next to ``default_registry_dir()`` when the caller
-    does not know its registry. The default registry is
-    ``$WORKSPACE_ROOT/.mam/jobs`` (Issue #15), otherwise ``<cwd>/.mam/jobs``,
-    so the usual roots are unchanged. Resolved per call rather than at import
-    so a chdir after import cannot strand the audit trail in the old tree —
-    the same reason ``DEFAULT_REGISTRY_DIR`` stays a relative string.
-    """
-    env = os.environ.get("DELEGATE_JOB_LOGS_DIR")
-    if env and env.strip():
-        return env
-    return sibling_logs_dir(registry_dir or default_registry_dir())
-
-
 def __getattr__(name: str):          # PEP 562 (3.7+)
     """Keep ``mqtt_common.LOGS_DIR`` working for external consumers
     (documented in registry.md) while resolving it dynamically."""
@@ -328,6 +283,9 @@ def make_client(role: str, config: Optional[BrokerConfig] = None) -> mqtt.Client
     """
     config = config or broker_config_from_env()
     client_id = f"{config.client_id_prefix}-{role}-{uuid.uuid4().hex[:8]}"
+    if mqtt is None:
+        raise ImportError("paho-mqtt is required to talk to a broker; install it into the virtualenv "
+                          "(see multi-agent-mux-delegate-job/requirements.txt)")
     client = mqtt.Client(
         callback_api_version=mqtt.CallbackAPIVersion.VERSION2,
         client_id=client_id,