[client] launch macOS GUI as the logged-in user after install/update (#6962)

## Describe your changes

In unattended installs/updates there may be no logged-in user, so
there's no context to start the GUI (nor anyone to see it).

The bug is the GUI being started in the wrong user context / inheriting
the wrong `$HOME` (OS mechanics aside).

Today the GUI is started by a per-user LaunchAgent, i.e. on behalf of
the user who logs in — no login ⇒ no GUI.

The patch aligns to this: it launches the GUI on behalf of the logged-in
console user if one exists, otherwise it delegates the launch to the
per-user LaunchAgent at next login.

Additionally it logs when default UI settings are applied.

Note (small caveat): the LaunchAgent auto-starts the GUI at login only
once it's been registered — which happens on the first GUI launch in the
user's context. On an MDM/unattended fresh install done with no user
logged in (where the user has never run the GUI before), they may need
to start it manually once; it self-registers from then on.

## Issue ticket number and link

No public issue — reported internally (community report on Slack: macOS
advanced-view + onboarding reset on every update, esp. via MDM/Munki).
Buggy line on main:
dd2bdc0de3/release_files/darwin_pkg/postinstall (L33)

## Stack

<!-- branch-stack -->

### Checklist
- [x] Is it a bug fix
- [ ] Is a typo/documentation fix
- [ ] Is a feature enhancement
- [ ] It is a refactor
- [ ] Created tests that fail without the change (if possible)

> By submitting this pull request, you confirm that you have read and
agree to the terms of the [Contributor License
Agreement](https://github.com/netbirdio/netbird/blob/main/CONTRIBUTOR_LICENSE_AGREEMENT.md).

## Documentation
Select exactly one:

- [ ] I added/updated documentation for this change
- [x] Documentation is **not needed** for this change (explain why)

Internal macOS installer / GUI-launch behavior. No public API, CLI, or
configuration change: the fix only changes the user context the desktop
GUI is launched in after a pkg install/update.

### Docs PR URL (required if "docs added" is checked)
Paste the PR link from https://github.com/netbirdio/docs here:

N/A

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<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

- **Bug Fixes**
- Improved macOS installation and updater UI launching to occur only
when an active, valid GUI console session is detected.
- Prevented UI launches during unattended/system, root, or
login-window-related installs.
- Ensured the app is launched in the correct console-user context, and
skips cleanly when username/UID resolution fails.

- **Improvements**
- Added clearer informational logging when the UI preferences file is
not found and default preferences are used.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

client/internal/updater/installer/installer_run_darwin.go

@@ -98,47 +98,44 @@ func (u *Installer) startDaemon(daemonFolder string) error {
 func (u *Installer) startUIAsUser() error {
 	log.Infof("starting netbird-ui: %s", uiBinary)
 
-	// Get the current console user
-	cmd := exec.Command("stat", "-f", "%Su", "/dev/console")
-	output, err := cmd.Output()
+	username, err := consoleUser()
 	if err != nil {
-		return fmt.Errorf("failed to get console user: %w", err)
+		return err
 	}
 
-	username := strings.TrimSpace(string(output))
-	if username == "" || username == "root" {
-		return fmt.Errorf("no active user session found")
-	}
-
-	log.Infof("starting UI for user: %s", username)
-
-	// Get user's UID
 	userInfo, err := user.Lookup(username)
 	if err != nil {
-		return fmt.Errorf("failed to lookup user %s: %w", username, err)
+		return fmt.Errorf("lookup user %s: %w", username, err)
 	}
 
-	// Start the UI process as the console user using launchctl
-	// This ensures the app runs in the user's context with proper GUI access
-	launchCmd := exec.Command("launchctl", "asuser", userInfo.Uid, "open", "-a", uiBinary)
+	log.Infof("starting UI for user: %s (uid %s)", username, userInfo.Uid)
+
+	launchCmd := exec.Command("launchctl", "asuser", userInfo.Uid, "sudo", "-u", username, "-H", "open", "-a", uiBinary)
 	log.Infof("launchCmd: %s", launchCmd.String())
-	// Set the user's home directory for proper macOS app behavior
-	launchCmd.Env = append(os.Environ(), "HOME="+userInfo.HomeDir)
-	log.Infof("set HOME environment variable: %s", userInfo.HomeDir)
 
-	if err := launchCmd.Start(); err != nil {
-		return fmt.Errorf("failed to start UI process: %w", err)
-	}
-
-	// Release the process so it can run independently
-	if err := launchCmd.Process.Release(); err != nil {
-		log.Warnf("failed to release UI process: %v", err)
+	if err := launchCmd.Run(); err != nil {
+		return fmt.Errorf("run UI launch: %w", err)
 	}
 
 	log.Infof("netbird-ui started successfully for user %s", username)
 	return nil
 }
 
+func consoleUser() (string, error) {
+	output, err := exec.Command("stat", "-f", "%Su", "/dev/console").Output()
+	if err != nil {
+		return "", fmt.Errorf("get console user: %w", err)
+	}
+
+	username := strings.TrimSpace(string(output))
+	switch username {
+	case "", "root", "loginwindow", "_mbsetupuser":
+		return "", fmt.Errorf("no active GUI user session, console user: %q", username)
+	}
+
+	return username, nil
+}
+
 func (u *Installer) installPkgFile(ctx context.Context, path string) error {
 	log.Infof("installing pkg file: %s", path)
 

client/ui/preferences/store.go

@@ -246,6 +246,7 @@ func (s *Store) ExistedAtLoad() bool {
 func (s *Store) load() error {
 	if _, err := os.Stat(s.path); err != nil {
 		if errors.Is(err, os.ErrNotExist) {
+			log.Infof("no ui preferences file at %s; using defaults", s.path)
 			return nil
 		}
 		return fmt.Errorf("stat preferences: %w", err)

release_files/darwin_pkg/postinstall

@@ -30,7 +30,23 @@ mkdir -p /usr/local/bin/
     $AGENT service install || true
     $AGENT service start || true
 
-    open $APP
+    console_user=$(stat -f%Su /dev/console 2>/dev/null)
+    case "$console_user" in
+        ""|root|loginwindow|_mbsetupuser)
+            echo "No active GUI user session (console user: '${console_user:-none}'); skipping UI launch."
+            ;;
+        *)
+            uid=$(id -u "$console_user" 2>/dev/null)
+            if [ -z "$uid" ]; then
+                echo "Could not resolve uid for console user '$console_user'; skipping UI launch."
+            else
+                echo "Launching NetBird UI as console user $console_user (uid $uid)."
+                if ! launchctl asuser "$uid" sudo -u "$console_user" -H open "$APP"; then
+                    echo "Failed to launch NetBird UI; if autostart is enabled it will start at next login."
+                fi
+            fi
+            ;;
+    esac
 
     echo "Finished Netbird installation successfully"
     exit 0 # all good