Feat: Implement memory feature for last selected environment

config.go

@@ -398,5 +398,32 @@ func removeEnvironmentFromConfig(config *Config, name string) error {
 
 	// Remove environment by copying elements
 	config.Environments = append(config.Environments[:index], config.Environments[index+1:]...)
+
+	// Clear last selected if it was the removed environment
+	if config.LastSelected == name {
+		config.LastSelected = ""
+	}
+
 	return nil
 }
+
+// updateLastSelected updates the last selected environment in the configuration
+func updateLastSelected(config *Config, envName string) {
+	// Only update if the environment exists
+	if _, exists := findEnvironmentByName(*config, envName); exists {
+		config.LastSelected = envName
+	}
+}
+
+// getLastSelectedIndex returns the index of the last selected environment, or 0 if not found
+func getLastSelectedIndex(config Config) int {
+	if config.LastSelected == "" {
+		return 0 // Default to first environment
+	}
+
+	if index, exists := findEnvironmentByName(config, config.LastSelected); exists {
+		return index
+	}
+
+	return 0 // Default to first environment if last selected not found
+}

main.go

@@ -100,6 +100,7 @@ type Environment struct {
 // Config represents the complete configuration with all environments
 type Config struct {
 	Environments []Environment   `json:"environments"`
+	LastSelected string            `json:"last_selected,omitempty"`
 	Settings     *ConfigSettings `json:"settings,omitempty"`
 }
 
@@ -729,6 +730,13 @@ func runDefaultWithOverride(envName string, claudeArgs []string, keyVarOverride
 		if err != nil {
 			return fmt.Errorf("environment selection failed: %w", err)
 		}
+
+		// Save last selected environment
+		updateLastSelected(&config, selectedEnv.Name)
+		if err := saveConfig(config); err != nil {
+			// Non-fatal error - continue with execution but log warning
+			fmt.Fprintf(os.Stderr, "Warning: failed to save last selected environment: %v\n", err)
+		}
 	}
 
 	// Apply one-run override if provided