fix: harden operations and configuration recovery

internal/shell/shell.go

@@ -323,8 +323,19 @@ func (a *Adapter) disable() error {
 	if metadata.OriginalScript != nil {
 		restored = []byte(*metadata.OriginalScript)
 	}
-	if err := a.writeOwned(a.configuration.EnvironmentFile, restored); err != nil {
-		return fmt.Errorf("restore Shell environment: %w", err)
+	current, err := a.files.ReadFile(a.configuration.EnvironmentFile)
+	if err != nil {
+		return fmt.Errorf("read managed Shell environment before restore: %w", err)
+	}
+	switch currentFingerprint := fingerprint(current); currentFingerprint {
+	case fingerprint(restored):
+		// A previous recovery completed the file write but not metadata cleanup.
+	case metadata.Fingerprint:
+		if err := a.writeOwned(a.configuration.EnvironmentFile, restored); err != nil {
+			return fmt.Errorf("restore Shell environment: %w", err)
+		}
+	default:
+		return errors.New("Shell environment changed after proxyctl applied it; refusing to overwrite current configuration or discard recovery metadata")
 	}
 	if err := a.files.Remove(a.configuration.RecoveryFile); err != nil && !errors.Is(err, fs.ErrNotExist) {
 		return fmt.Errorf("remove Shell recovery metadata after environment changed: %w", err)