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

lib/instance/ensure.go

@@ -1,9 +1,18 @@
 package instance
 
-// EnsureRunning starts a detached agent if none is holding the mutex.
+import (
+	"tea.chunkbyte.com/kato/go-worm/lib/config"
+)
+
+// EnsureRunning starts this host's agent if none is holding the mutex.
+// Callers that can stay resident should run the agent in-process instead.
 func EnsureRunning() error {
 	if AlreadyRunning() {
 		return nil
 	}
-	return Detach()
+	exe, err := config.InstalledExe()
+	if err != nil {
+		return err
+	}
+	return Launch(exe, nil)
 }