With the daemon shipped as a systemd user unit, the CLI must not fight
systemd for it:
- Auto-start (DaemonClient::startDaemon): when the unit is installed but
not running and would run exactly the daemon the client expects (same
socket, data dir and config as the default resolution, default
binary), start it with `systemctl --user start` instead of forking a
copy that a later login would race for the socket. Flag or
environment overrides (--socket, --data-dir, YAMS_DAEMON_SOCKET,
YAMS_DATA_DIR, YAMS_CONFIG, YAMS_DAEMON_BIN) keep the fork path.
- `yams daemon start|stop|restart` use `systemctl --user` for an
installed/active unit (start/restart without custom path options,
stop/restart without --socket), falling back to IPC if systemctl
fails.
- `yams daemon install --user` with no options enables the packaged unit
(`systemctl --user enable --now`) instead of writing a copy into
~/.config/systemd/user that would shadow it; with options it still
writes that override and says so. `uninstall --user` reloads the
manager after removing an override and explains how to mask the
globally enabled packaged unit for one account.
The decision is a pure function (userUnitMatchesPaths) with Catch2
coverage; systemctl is only run with whitelisted verbs and only when a
user manager is reachable ($XDG_RUNTIME_DIR set, Linux).
Signed-off-by: trvon <me@trevon.dev>
