Fix critical bug: copilot signals were never connected

Root cause: Signal connection logic had a fatal flaw:
- Line 1328 set _copilot_signals_connected = True BEFORE calling _connect_copilot_signals()
- _connect_copilot_signals() checks this flag and returns early if True
- Result: Signals NEVER got connected on first call!

This explains why chat (and likely edit/create) buttons showed no response:
- UI emitted signals properly
- But no handlers were listening because connections failed silently

Fix applied:
- Changed condition from "if not hasattr" to "if not hasattr OR not value"
- Now properly checks both existence AND value of the flag
- Signals will connect on first toggle of copilot panel

This was preventing ALL copilot functionality from working.

Co-authored-by: HeDaas-Code <208586641+HeDaas-Code@users.noreply.github.com>

Author: Copilot

src/views/main_window.py

@@ -1324,8 +1324,7 @@ def toggleCopilotPanel(self):
                 self._copilot_signals_lock = threading.Lock()
 
             with self._copilot_signals_lock:
-                if not hasattr(self, '_copilot_signals_connected'):
-                    self._copilot_signals_connected = True
+                if not hasattr(self, '_copilot_signals_connected') or not self._copilot_signals_connected:
                     self._connect_copilot_signals()
         else:
             info("Copilot面板已隐藏")