refactor(gui): redesign ai settings layout and fix model fetching sync

src/app_controller.py

@@ -883,6 +883,8 @@ class AppController:
   self.persona_manager = PersonaManager(Path(self.active_project_path).parent if self.active_project_path else None)
   self.personas = self.persona_manager.load_all()
 
+  self._fetch_models(self.current_provider)
+
   self.ui_active_tool_preset = os.environ.get('SLOP_TOOL_PRESET') or ai_cfg.get("active_tool_preset")
   self.ui_active_bias_profile = ai_cfg.get("active_bias_profile")
   ai_client.set_tool_preset(self.ui_active_tool_preset)
@@ -1496,6 +1498,9 @@ class AppController:
    self._current_provider = value
    ai_client.reset_session()
    ai_client.set_provider(value, self.current_model)
+   self.available_models = self.all_available_models.get(value, [])
+   if not self.available_models:
+    self._fetch_models(value)
    self._token_stats = {}
    self._token_stats_dirty = True