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

.agents/skills/multi-agent-mux-delegate-job/scripts/mqtt_common.py

@@ -128,20 +128,30 @@ EVENTS_FILENAME = "events.ndjson"
 STATUS_FILENAME = "status.json"
 
 
-def _default_logs_dir() -> str:
-    """Audit-log root. Overridable with ``DELEGATE_JOB_LOGS_DIR``; otherwise
-    ``<cwd>/.mam/delegate_job_logs`` — we keep audit logs next to the
-    live registry (``.mam/jobs/``) so the two runtime artifacts sit
-    under the same parent dir and follow the same ``.gitignore`` rule.
-    The cwd of whichever process emits events (the bash wrapper and
-    scripts) is used as the anchor."""
+def get_logs_dir() -> str:
+    """Audit-log root, resolved at call time (B-9).
+
+    Overridable with ``DELEGATE_JOB_LOGS_DIR``; otherwise
+    ``<cwd>/.mam/delegate_job_logs``. 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 os.path.join(os.getcwd(), ".mam", "delegate_job_logs")
 
 
-LOGS_DIR = _default_logs_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."""
+    if name == "LOGS_DIR":
+        return get_logs_dir()
+    raise AttributeError(f"module {__name__!r} has no attribute {name!r}")
+
+
+def __dir__():                        # PEP 562 recommendation — keep dir()/tab-completion discoverable
+    return sorted(set(globals()) | {"LOGS_DIR"})
 
 
 # --------------------------------------------------------------------------
@@ -428,7 +438,7 @@ def _utcnow_precise() -> str:
 # touched (it is reserved for data output).
 # --------------------------------------------------------------------------
 def job_log_dir(job_id: str, logs_dir: Optional[str] = None) -> Path:
-    return Path(logs_dir or LOGS_DIR) / job_id
+    return Path(logs_dir or get_logs_dir()) / job_id
 
 
 def job_log_path(job_id: str, kind: str, logs_dir: Optional[str] = None) -> Path:
@@ -576,7 +586,7 @@ def iter_logged_events(job_id: str, logs_dir: Optional[str] = None):
 def list_logged_jobs(logs_dir: Optional[str] = None) -> List[Dict[str, Any]]:
     """Return one meta record per job directory under the logs root, oldest
     first. Falls back to ``{"job_id": <dir>}`` when meta.json is missing."""
-    base = Path(logs_dir or LOGS_DIR)
+    base = Path(logs_dir or get_logs_dir())
     out: List[Dict[str, Any]] = []
     if not base.exists():
         return out

.agents/skills/multi-agent-mux-delegate-job/scripts/registry.py

@@ -195,7 +195,7 @@ def get_feedback(job_id: str, registry_dir: str = DEFAULT_REGISTRY_DIR) -> str:
     # 1) Try the unified audit log first (ndjson) since it's written synchronously by the subscriber
     try:
         import mqtt_common
-        logs_dir = mqtt_common.LOGS_DIR
+        logs_dir = mqtt_common.get_logs_dir()
         events = list(mqtt_common.iter_logged_events(job_id, logs_dir))
         for e in reversed(events):
             if e.get("source_event") in ("completed", "error"):
@@ -386,7 +386,7 @@ def main(argv: Optional[List[str]] = None) -> int:
 
 def _cmd_logs(args) -> int:
     """Pretty-print one job's events.ndjson, or summarise all logged jobs."""
-    logs_dir = args.logs_dir or mqtt_common.LOGS_DIR
+    logs_dir = args.logs_dir or mqtt_common.get_logs_dir()
 
     if args.list_all:
         jobs = mqtt_common.list_logged_jobs(logs_dir)