Fix language model selector (#26138)

This PR fixes the language model selector.

I tried to piece together the state prior to #25697 (the state it was in
at 11838cf89e) while retaining unrelated
changes that happened since then.

Release Notes:

- Fixed an issue where language models would not be authenticated until
after the model selector was opened (Preview only).

crates/assistant2/src/message_editor.rs

@@ -54,6 +54,7 @@ impl MessageEditor {
         let context_store = cx.new(|_cx| ContextStore::new(workspace.clone()));
         let context_picker_menu_handle = PopoverMenuHandle::default();
         let inline_context_picker_menu_handle = PopoverMenuHandle::default();
+        let model_selector_menu_handle = PopoverMenuHandle::default();
 
         let editor = cx.new(|cx| {
             let mut editor = Editor::auto_height(10, window, cx);
@@ -106,8 +107,15 @@ impl MessageEditor {
             context_picker_menu_handle,
             inline_context_picker,
             inline_context_picker_menu_handle,
-            model_selector: cx
-                .new(|cx| AssistantModelSelector::new(fs, editor.focus_handle(cx), window, cx)),
+            model_selector: cx.new(|cx| {
+                AssistantModelSelector::new(
+                    fs,
+                    model_selector_menu_handle,
+                    editor.focus_handle(cx),
+                    window,
+                    cx,
+                )
+            }),
             use_tools: false,
             _subscriptions: subscriptions,
         }