Fix creating new conversations in the assistant via cmd-n

Co-Authored-By: Marshall <marshall@zed.dev>

assets/keymaps/default.json

@@ -189,6 +189,7 @@
   {
     "context": "AssistantPanel",
     "bindings": {
+      "cmd-n": "assistant::NewConversation",
       "cmd-g": "search::SelectNextMatch",
       "cmd-shift-g": "search::SelectPrevMatch"
     }

crates/assistant/src/assistant_panel.rs

@@ -86,9 +86,7 @@ actions!(
 pub fn init(cx: &mut AppContext) {
     settings::register::<AssistantSettings>(cx);
     cx.add_action(
-        |this: &mut AssistantPanel,
-         _: &workspace::NewFile,
-         cx: &mut ViewContext<AssistantPanel>| {
+        |this: &mut AssistantPanel, _: &NewConversation, cx: &mut ViewContext<AssistantPanel>| {
             this.new_conversation(cx);
         },
     );