fn memory_dir_from_registry(agent_id: &str) -> Option<PathBuf>Expand description
Resolve a memory dir for agent_id from the global named-agent registry.
Each live agent is recorded by instance_name with a working_dir relative
to source_agents_base (the channel/dev instance it lives in) and an
identity_id that determines its CLAUDE_CONFIG_DIR root. Returns None
when the registry is unavailable or no active record matches the slug.