add yamaha speaker discovery via tcp:50000 and move pollNode to tendrils.go

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

yamaha.go

@@ -0,0 +1,36 @@
+package tendrils
+
+import (
+	"bufio"
+	"log"
+	"net"
+	"regexp"
+	"time"
+)
+
+var yamahaModelRegex = regexp.MustCompile(`PA-Platform:ModelId\s*=\s*0x[0-9a-fA-F]+\(([^)]+)\)`)
+
+func (t *Tendrils) probeYamahaDevice(ip net.IP) string {
+	conn, err := net.DialTimeout("tcp", net.JoinHostPort(ip.String(), "50000"), 2*time.Second)
+	if err != nil {
+		return ""
+	}
+	defer conn.Close()
+
+	conn.SetReadDeadline(time.Now().Add(2 * time.Second))
+
+	scanner := bufio.NewScanner(conn)
+	for scanner.Scan() {
+		line := scanner.Text()
+		if match := yamahaModelRegex.FindStringSubmatch(line); match != nil {
+			model := match[1]
+			if t.DebugYamaha {
+				log.Printf("[yamaha] %s: found model %s", ip, model)
+			}
+			t.nodes.Update(nil, nil, []net.IP{ip}, "", model, "yamaha")
+			return model
+		}
+	}
+
+	return ""
+}