refactor(core): add headless run and auto-restart

- Run without console by default
- Log to file once console hidden
- Recover panics in background goroutines
- Restart agent after unexpected errors
- Use shared instance launch helper

lib/helpers/logfile.go

@@ -0,0 +1,25 @@
+package helpers
+
+import (
+	"os"
+	"path/filepath"
+
+	"tea.chunkbyte.com/kato/go-worm/lib/config"
+)
+
+// AttachLogFile appends application logs to logs/agent.log.
+func AttachLogFile() error {
+	dir, err := config.LogsDir()
+	if err != nil {
+		return err
+	}
+	if err := os.MkdirAll(dir, 0o700); err != nil {
+		return err
+	}
+	f, err := os.OpenFile(filepath.Join(dir, "agent.log"), os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0o600)
+	if err != nil {
+		return err
+	}
+	SetLogOutput(f)
+	return nil
+}