Implement serialization of assistant conversations, including tool calls and attachments (#11577)

Release Notes:

- N/A

---------

Co-authored-by: Kyle <kylek@zed.dev>
Co-authored-by: Marshall <marshall@zed.dev>

crates/assistant2/src/tools/create_buffer.rs

@@ -86,7 +86,8 @@ impl LanguageModelTool for CreateBufferTool {
         })
     }
 
-    fn output_view(
+    fn view(
+        &self,
         input: Self::Input,
         output: Result<Self::Output>,
         cx: &mut WindowContext,