New revision of the Assistant Panel (#10870)

This is a crate only addition of a new version of the AssistantPanel.
We'll be putting this behind a feature flag while we iron out the new
experience.

Release Notes:

- N/A

---------

Co-authored-by: Nathan Sobo <nathan@zed.dev>
Co-authored-by: Antonio Scandurra <me@as-cii.com>
Co-authored-by: Conrad Irwin <conrad@zed.dev>
Co-authored-by: Marshall Bowers <elliott.codes@gmail.com>
Co-authored-by: Antonio Scandurra <antonio@zed.dev>
Co-authored-by: Nate Butler <nate@zed.dev>
Co-authored-by: Nate Butler <iamnbutler@gmail.com>
Co-authored-by: Max Brunsfeld <maxbrunsfeld@gmail.com>
Co-authored-by: Max <max@zed.dev>

crates/assistant/src/completion_provider/open_ai.rs

@@ -140,14 +140,24 @@ impl OpenAiCompletionProvider {
             messages: request
                 .messages
                 .into_iter()
-                .map(|msg| RequestMessage {
-                    role: msg.role.into(),
-                    content: msg.content,
+                .map(|msg| match msg.role {
+                    Role::User => RequestMessage::User {
+                        content: msg.content,
+                    },
+                    Role::Assistant => RequestMessage::Assistant {
+                        content: Some(msg.content),
+                        tool_calls: Vec::new(),
+                    },
+                    Role::System => RequestMessage::System {
+                        content: msg.content,
+                    },
                 })
                 .collect(),
             stream: true,
             stop: request.stop,
             temperature: request.temperature,
+            tools: Vec::new(),
+            tool_choice: None,
         }
     }
 }