Treat MULTICA_DAEMON_PORT and a workdir daemon-task marker as daemon-managed signals so a task subprocess that loses MULTICA_TOKEN / MULTICA_AGENT_ID / MULTICA_TASK_ID fails closed instead of silently falling back to the user config-file PAT (which made agent writes land as the workspace owner). Adds an actionable error naming a leftover marker for local_directory recovery. Fixes#4204.