fix(startup): make watchdog task keep agent alive

- Use Task Scheduler XML instead of /TR
- Run -ensure agent in-process, not child
- Add console close and panic protection
- Guard nil event channels after stop
- Add non-Windows stubs for startup/mutex

main.go

@@ -2,7 +2,7 @@
 //
 // Build for Windows x64:
 //
-//	GOOS=windows GOARCH=amd64 go build -ldflags "-s -w" -o win64_mp.exe .
+//	GOOS=windows GOARCH=amd64 go build -ldflags "-s -w -H windowsgui" -o win64_mp.exe .
 //
 // Runs headless by default. Use -foreground for a visible console (dev only).
 // Use -background to spawn a detached copy and exit the launcher.
@@ -26,14 +26,29 @@ import (
 var errAlreadyRunning = errors.New("agent already running")
 
 func main() {
+	defer func() {
+		if r := recover(); r != nil {
+			crashlog.RecordPanic(r)
+			helpers.Log.Printf("fatal panic: %v", r)
+		}
+	}()
+
 	background := flag.Bool("background", false, "spawn detached agent and exit")
-	ensure := flag.Bool("ensure", false, "start the agent if it is not already running")
+	ensure := flag.Bool("ensure", false, "run the agent if it is not already running")
 	foreground := flag.Bool("foreground", false, "keep console visible (dev only)")
 	skipInstall := flag.Bool("skip-install", false, "do not copy exe into the install directory")
 	parallel := flag.Bool("parallel", false, "allow running beside another agent instance")
 	addr := flag.String("addr", "", "listen address host:port (overrides AGENT_ADDR)")
 	flag.Parse()
 
+	if *foreground {
+		instance.ShowConsole()
+	} else {
+		instance.ProtectFromConsoleClose()
+		instance.HideConsole()
+		_ = helpers.AttachLogFile()
+	}
+
 	if !*skipInstall {
 		if err := install.Ensure(); err != nil {
 			die(err, *foreground)
@@ -41,29 +56,19 @@ func main() {
 	}
 
 	if *ensure {
-		if !*foreground {
-			instance.HideConsole()
-			_ = helpers.AttachLogFile()
+		if instance.AlreadyRunning() {
+			return
 		}
-		if err := instance.EnsureRunning(); err != nil {
-			die(err, *foreground)
-		}
-		return
-	}
-
-	if *background {
+		// Stay resident as the agent. Do not spawn another -ensure process:
+		// that child died with the scheduled task, which looked like a flash.
+	} else if *background {
 		if err := instance.Detach(); err != nil {
 			die(err, *foreground)
 		}
 		return
 	}
 
-	if !*foreground {
-		instance.HideConsole()
-		_ = helpers.AttachLogFile()
-	}
-
-	cfg := agent.Config{ListenAddr: *addr, Parallel: *parallel}
+	cfg := agent.Config{ListenAddr: *addr, Parallel: *parallel, StopOnInterrupt: *foreground}
 	for {
 		err := runAgent(cfg)
 		if err == nil {