ax(mining): replace copy builtin shadow with settingsCopy, comment as usage example

AX Principle 1 — predictable names over short names: variable `copy` shadows
the Go builtin and carries no semantic meaning. Renamed to `settingsCopy`.
AX Principle 2 — comments as usage examples: replaced prose description on
SettingsManager.Get with a concrete call showing how the return value is used.

Co-Authored-By: Charon <charon@lethean.io>

pkg/mining/settings_manager.go

@@ -150,14 +150,15 @@ func (sm *SettingsManager) Save() error {
 	return os.WriteFile(sm.settingsPath, data, 0600)
 }
 
-// Get returns a copy of the current settings
+// settings := sm.Get()
+// if settings.Theme == "dark" { ... }
 func (sm *SettingsManager) Get() *AppSettings {
 	sm.mu.RLock()
 	defer sm.mu.RUnlock()
 
 	// Return a copy to prevent concurrent modification
-	copy := *sm.settings
-	return &copy
+	settingsCopy := *sm.settings
+	return &settingsCopy
 }
 
 // Update applies changes to settings and saves