feat(config): wire serial tool into runtime and dashboard

pkg/agent/agent_init.go

@@ -128,6 +128,9 @@ func registerSharedTools(
 		if cfg.Tools.IsToolEnabled("spi") {
 			agent.Tools.Register(tools.NewSPITool())
 		}
+		if cfg.Tools.IsToolEnabled("serial") {
+			agent.Tools.Register(tools.NewSerialTool())
+		}
 
 		// Message tool
 		if cfg.Tools.IsToolEnabled("message") {

pkg/config/config.go

@@ -823,6 +823,7 @@ type ToolsConfig struct {
 	ListDir         ToolConfig         `json:"list_dir"          yaml:"-"                                                       envPrefix:"PICOCLAW_TOOLS_LIST_DIR_"`
 	Message         ToolConfig         `json:"message"           yaml:"-"                                                       envPrefix:"PICOCLAW_TOOLS_MESSAGE_"`
 	ReadFile        ReadFileToolConfig `json:"read_file"         yaml:"-"                                                       envPrefix:"PICOCLAW_TOOLS_READ_FILE_"`
+	Serial          ToolConfig         `json:"serial"            yaml:"-"                                                       envPrefix:"PICOCLAW_TOOLS_SERIAL_"`
 	SendFile        ToolConfig         `json:"send_file"         yaml:"-"                                                       envPrefix:"PICOCLAW_TOOLS_SEND_FILE_"`
 	SendTTS         ToolConfig         `json:"send_tts"          yaml:"-"                                                       envPrefix:"PICOCLAW_TOOLS_SEND_TTS_"`
 	Spawn           ToolConfig         `json:"spawn"             yaml:"-"                                                       envPrefix:"PICOCLAW_TOOLS_SPAWN_"`
@@ -1548,6 +1549,8 @@ func (t *ToolsConfig) IsToolEnabled(name string) bool {
 		return t.Message.Enabled
 	case "read_file":
 		return t.ReadFile.Enabled
+	case "serial":
+		return t.Serial.Enabled
 	case "spawn":
 		return t.Spawn.Enabled
 	case "spawn_status":

pkg/config/defaults.go

@@ -435,6 +435,9 @@ func DefaultConfig() *Config {
 				Mode:            ReadFileModeBytes,
 				MaxReadFileSize: 64 * 1024, // 64KB
 			},
+			Serial: ToolConfig{
+				Enabled: false, // Hardware tool - requires host serial ports
+			},
 			Spawn: ToolConfig{
 				Enabled: true,
 			},