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/uart/frame.go

@@ -4,6 +4,7 @@ import (
 	"errors"
 	"fmt"
 	"io"
+	"time"
 )
 
 const (
@@ -98,13 +99,22 @@ func (p *Parser) Feed(b byte) (payload []byte, ok bool, err error) {
 }
 
 // ReadFrame reads bytes from r until one full frame is parsed or an error occurs.
-func ReadFrame(r io.Reader, buf []byte) ([]byte, error) {
+// maxWait bounds total wait time; zero means no limit (serial read timeouts retry forever).
+func ReadFrame(r io.Reader, buf []byte, maxWait time.Duration) ([]byte, error) {
 	if buf == nil {
 		buf = make([]byte, 256)
 	}
 	parser := NewParser()
 
+	var deadline time.Time
+	if maxWait > 0 {
+		deadline = time.Now().Add(maxWait)
+	}
+
 	for {
+		if !deadline.IsZero() && !time.Now().Before(deadline) {
+			return nil, ErrTimeout
+		}
 		n, err := r.Read(buf)
 		if n > 0 {
 			for i := 0; i < n; i++ {