Fix latch file ownership after a root stop/resume without a running node; log files on macOS; honest log docs

ddiff --git a/cmd/openvibe-node/main.go b/cmd/openvibe-node/main.go
iindex e667771..c6ef81d 100644
---- a/cmd/openvibe-node/main.go
++++ b/cmd/openvibe-node/main.go
@@@ -331,6 +331,7 @@ func cmdStop(g *globals, stdout io.Writer) error {
  	if ferr := safety.WriteLocalFile(g.paths.LatchFile(), true); ferr != nil {
  		return fmt.Errorf("could not reach the node (%v) nor write %s (%v); run with sudo", err, g.paths.LatchFile(), ferr)
  	}
++	chownLikeDir(g.paths.LatchFile(), g.paths.StateDir) // the service account must be able to read it
  	fmt.Fprintln(stdout, "The node did not answer; the stop is latched in", g.paths.LatchFile())
  	fmt.Fprintln(stdout, "A running node obeys it within a quarter second; a starting node starts stopped. Release with `openvibe-node resume`.")
  	return nil
@@@ -342,6 +343,7 @@ func cmdResume(g *globals, stdout io.Writer) error {
  		if ferr := safety.WriteLocalFile(g.paths.LatchFile(), false); ferr != nil {
  			return fmt.Errorf("could not reach the node (%v) nor write %s (%v); run with sudo", err, g.paths.LatchFile(), ferr)
  		}
++		chownLikeDir(g.paths.LatchFile(), g.paths.StateDir)
  	}
  	fmt.Fprintln(stdout, "Resumed: the local stop and any server e-stop are released. Operators can drive again.")
  	return nil
ddiff --git a/docs/install.md b/docs/install.md
iindex 558ebbf..5049f6b 100644
---- a/docs/install.md
++++ b/docs/install.md
@@@ -128,7 +128,8 @@ internet (Ethernet, or a second Wi-Fi adapter). Install with `--robot cozmo`; th
  
  - `openvibe-node status` shows the last link error. "the server refused the device credential" means it was revoked:
    `sudo openvibe-node pair --force <NEW-CODE>`.
--- Logs: `journalctl -u openvibe-node -f` (Linux), `/var/log/openvibe-node.*.log` (macOS), Event Viewer (Windows).
++- Logs: `journalctl -u openvibe-node -f` (Linux), `/usr/local/var/log/openvibe-node.err.log` (macOS). On Windows the
++  service's log is not kept yet; stop the service and run `openvibe-node run` in a terminal to watch it.
  - A plugin in `faulted` state says why in `status` (missing library, not a Raspberry Pi, robot not reachable, firmware).
  - `openvibe-node plugins` works without the service running: it asks each plugin to describe itself without touching
    hardware.
ddiff --git a/internal/service/service.go b/internal/service/service.go
iindex 4429014..076df26 100644
---- a/internal/service/service.go
++++ b/internal/service/service.go
@@@ -5,6 +5,7 @@ package service
  import (
  	"context"
  	"errors"
++	"runtime"
  	"sync"
  	"time"
  
@@@ -73,7 +74,7 @@ type Options struct {
  }
  
  func config(opt Options) *ks.Config {
--	return &ks.Config{
++	c := &ks.Config{
  		Name: Name, DisplayName: DisplayName, Description: Description, Arguments: opt.Arguments, UserName: opt.UserName,
  		Option: ks.KeyValue{
  			"Restart":                "always", // systemd
@@@ -85,6 +86,11 @@ func config(opt Options) *ks.Config {
  			"DelayedAutoStart":       false,
  		},
  	}
++	if runtime.GOOS == "darwin" {
++		// launchd has no journal: write /usr/local/var/log/openvibe-node.{out,err}.log. systemd keeps journald.
++		c.Option["LogOutput"] = true
++	}
++	return c
  }
  
  // Run runs program under the service manager, or in the foreground when started from a terminal.