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/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)