Fix: send input cleared after successful send, breaking auto-send

[Copilot]

After every successful send, send_data() called self.send_input.clear(), wiping the input box. This broke auto-send (the timer's second tick would find an empty input and silently do nothing) and forced users to retype on every manual send.

Changes

• src/ui/main_window.py — remove self.send_input.clear() from send_data() so the input content persists after sending

# Before
if self.serial_manager.send_text(text, fmt):
    self.sent_bytes += len(text.encode('utf-8'))
    self.send_input.clear()   # ← cleared content, breaking auto-send

# After
if self.serial_manager.send_text(text, fmt):
    self.sent_bytes += len(text.encode('utf-8'))
    # input content preserved

• Fixes 发送数据后发送框内容会被清空 #1

[Copilot]

Copilot encountered an error and was unable to review this pull request. You can try again by re-requesting a review.