Krikri::SSHManager::DaemonKey

Perf items 1-3 (formerly SUGGESTED_PERFORMANCE_IMPROVEMENTS.md item #15, a doc since deleted) - the persistent remote executor's controller half. exec/exec_script above pay a fresh local ssh fork + remote process spawn on EVERY call, multiplexed over the same ControlMaster TCP session but never reusing the actual spawned processes. This instead keeps ONE ssh ... -- <fat-plugin> --daemon Process alive per (host, user, port) and speaks the length-prefixed protocol plugin_daemon.cr implements on the remote end directly over that process's own stdin/stdout pipes - every subsequent call is a plain write+read on an already-open pipe, no new process on either side.

Deliberately opt-in (only reached when PluginManager. daemon_enabled? is true) and only used for the SOLO, non-become remote-dispatch path - see PluginManager.daemon_eligible?'s own comment for exactly what's excluded and why. Keyed identically to @@control_path_cache above, same one-fiber-per-host safety argument executor.cr's own run_task_for_hosts_in_parallel comment already documents - a given host's daemon connection is never touched by two fibers at once, so no correlation ID or lock is needed on top of this Hash. Perf item 1: keyed on the become_user too, not just (host, user, port). A daemon is one resident process running as one fixed user, so become: true tasks cannot share the unprivileged host connection's daemon - but they can have their own, spawned as sudo -n -u <become_user> -- <binary> --daemon. A play mixing privileged and unprivileged tasks holds two resident daemons per host, which is fine. nil in the last slot is the no-become daemon.