Fix UART hang after master restart from the dashboard.

ReadFrame now returns on serial timeout instead of looping forever, and
serve closes and reopens the port after a master reboot so polling and
API commands can resume.

Co-authored-by: Cursor <cursoragent@cursor.com>

goTool/serial_link.go

@@ -105,6 +105,26 @@ func (m *managedSerial) withPortLocked(poll bool, fn func(*serialPort) error) er
 	return err
 }
 
+func (m *managedSerial) recoverAfterMasterRestart() {
+	const bootWait = 6 * time.Second
+
+	m.mu.Lock()
+	m.closeLocked()
+	m.mu.Unlock()
+
+	log.Printf("UART: master restart — waiting %s for boot", bootWait)
+	time.Sleep(bootWait)
+
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	if err := m.openLocked(); err != nil {
+		log.Printf("UART reconnect after master restart: %v", err)
+		return
+	}
+	flushSerialInput(m.sp)
+	log.Printf("UART %s ready after master restart", m.portName)
+}
+
 func (m *managedSerial) exchangePayload(payload []byte, cmdName string) ([]byte, error) {
 	return m.exchangePayloadVia(m.withPort, payload, cmdName)
 }