Harden config storage and fix concurrency/install checks

internal/config/config.go

@@ -89,7 +89,7 @@ func Save(c *Config, configPath string) error {
 
 	// Ensure the directory exists
 	dir := filepath.Dir(configPath)
-	if err := os.MkdirAll(dir, 0755); err != nil {
+	if err := os.MkdirAll(dir, 0700); err != nil {
 		return err
 	}
 
@@ -98,7 +98,7 @@ func Save(c *Config, configPath string) error {
 		return err
 	}
 
-	return os.WriteFile(configPath, data, 0644)
+	return os.WriteFile(configPath, data, 0600)
 }
 
 // GetConfigPath returns the default configuration file path.

internal/services/whisper/whisper.go

@@ -74,7 +74,12 @@ func (m *Manager) IsInstalled() bool {
 		return false
 	}
 
-	modelPath := filepath.Join(m.installDir, Models[info.Model].Filename)
+	modelInfo, ok := Models[info.Model]
+	if !ok || modelInfo.Filename == "" {
+		return false
+	}
+
+	modelPath := filepath.Join(m.installDir, modelInfo.Filename)
 	if _, err := os.Stat(modelPath); os.IsNotExist(err) {
 		return false
 	}
@@ -445,4 +450,3 @@ func downloadFile(url, dest string, progress chan<- DownloadProgress) error {
 	return nil
 }
 
-