OTA: answer once the announced image size has arrived

The Arduino network client treats a half-closed connection as closed,
so the device's reply after the sender's EOF was lost. The header
already carries the image size: UpdateParser::complete() lets the
device finish and answer while the connection is open. ota_push.py
half-closes only if no answer comes within 3 s, for older firmware.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EhqxQ49eCju4CzKYNjZzwT

scripts/ota_push.py

@@ -17,16 +17,29 @@ def main():
     data = open(path, "rb").read()
     with socket.create_connection((host, PORT), timeout=15) as s:
         s.settimeout(60)
-        sent = 0
+        sent, last = 0, -1
         while sent < len(data):
             chunk = data[sent:sent + 4096]
             s.sendall(chunk)
             sent += len(chunk)
-            print(f"\rsending {sent * 100 // len(data):3d}%", end="", flush=True)
-        s.shutdown(socket.SHUT_WR)  # end of file: the device checks it and answers
+            pct = sent * 100 // len(data)
+            if pct != last:
+                print(f"\rsending {pct:3d}%", end="", flush=True)
+                last = pct
+        # The header announces the image size, so current firmware answers once it has it all.
+        # Firmware from before that change only knows the file ended when we half-close.
         reply = b""
-        while not reply.endswith(b"\n"):
-            part = s.recv(256)
+        s.settimeout(3)
+        try:
+            reply = s.recv(256)
+        except socket.timeout:
+            s.shutdown(socket.SHUT_WR)
+            s.settimeout(60)
+        while reply == b"" or not reply.endswith(b"\n"):
+            try:
+                part = s.recv(256)
+            except socket.timeout:
+                break
             if not part:
                 break
             reply += part