gtksettings: fix NameError in ww_load error lambda (Python 3.12 scoping)

In Python 3.12 the 'except ... as e' variable is deleted after the except
block exits, so a plain lambda that closes over 'e' raises NameError when
GLib fires it later. Bind e as a default argument at lambda creation time.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

linux/blitztext/gtksettings.py

@@ -1070,7 +1070,7 @@ class SettingsDialog:
                         self._info("Loaded models successfully.")
                     GLib.idle_add(apply)
             except Exception as e:
-                GLib.idle_add(lambda: self._error(f"Failed to load models:\n{e}"))
+                GLib.idle_add(lambda e=e: self._error(f"Failed to load models:\n{e}"))
         threading.Thread(target=work, daemon=True).start()
 
     def _ww_test(self, _b) -> None: