feat(agent): add persistent klogging settings

- Add settings API and UI to toggle keylog
- Persist preference in settings.json
- Expose klogging state in status endpoint
- Inject build version into web console
- Bump version automatically on build

lib/config/settings.go

@@ -0,0 +1,75 @@
+package config
+
+import (
+	"encoding/json"
+	"os"
+	"path/filepath"
+)
+
+type fileSettings struct {
+	Klogging      *bool `json:"klogging,omitempty"`
+	KeylogEnabled *bool `json:"keylog_enabled,omitempty"` // legacy
+}
+
+func settingsPath() (string, error) {
+	dir, err := InstallDir()
+	if err != nil {
+		return "", err
+	}
+	return filepath.Join(dir, SettingsFileName), nil
+}
+
+func readKeylogPref() (bool, bool) {
+	s, err := loadFileSettings()
+	if err != nil {
+		return false, false
+	}
+	if s.Klogging != nil {
+		return *s.Klogging, true
+	}
+	if s.KeylogEnabled != nil {
+		return *s.KeylogEnabled, true
+	}
+	return false, false
+}
+
+func SetKeylogEnabled(on bool) error {
+	s, err := loadFileSettings()
+	if err != nil && !os.IsNotExist(err) {
+		s = fileSettings{}
+	}
+	s.Klogging = &on
+	s.KeylogEnabled = nil
+	return saveFileSettings(s)
+}
+
+func loadFileSettings() (fileSettings, error) {
+	path, err := settingsPath()
+	if err != nil {
+		return fileSettings{}, err
+	}
+	raw, err := os.ReadFile(path)
+	if err != nil {
+		return fileSettings{}, err
+	}
+	var s fileSettings
+	if err := json.Unmarshal(raw, &s); err != nil {
+		return fileSettings{}, err
+	}
+	return s, nil
+}
+
+func saveFileSettings(s fileSettings) error {
+	path, err := settingsPath()
+	if err != nil {
+		return err
+	}
+	if err := os.MkdirAll(filepath.Dir(path), 0o700); err != nil {
+		return err
+	}
+	raw, err := json.Marshal(s)
+	if err != nil {
+		return err
+	}
+	return os.WriteFile(path, append(raw, '\n'), 0o600)
+}