feat: add device hotplug event notifications (USB on Linux)

pkg/config/config.go

@@ -50,6 +50,7 @@ type Config struct {
 	Gateway   GatewayConfig   `json:"gateway"`
 	Tools     ToolsConfig     `json:"tools"`
 	Heartbeat HeartbeatConfig `json:"heartbeat"`
+	Devices   DevicesConfig   `json:"devices"`
 	mu        sync.RWMutex
 }
 
@@ -150,6 +151,11 @@ type HeartbeatConfig struct {
 	Interval int  `json:"interval" env:"PICOCLAW_HEARTBEAT_INTERVAL"` // minutes, min 5
 }
 
+type DevicesConfig struct {
+	Enabled    bool `json:"enabled" env:"PICOCLAW_DEVICES_ENABLED"`
+	MonitorUSB bool `json:"monitor_usb" env:"PICOCLAW_DEVICES_MONITOR_USB"`
+}
+
 type ProvidersConfig struct {
 	Anthropic    ProviderConfig `json:"anthropic"`
 	OpenAI       ProviderConfig `json:"openai"`
@@ -299,6 +305,10 @@ func DefaultConfig() *Config {
 			Enabled:  true,
 			Interval: 30, // default 30 minutes
 		},
+		Devices: DevicesConfig{
+			Enabled:    false,
+			MonitorUSB: true,
+		},
 	}
 }