Start on adding support for editing via the assistant panel (#14795)

Note that this shouldn't have any visible user-facing behavior yet. The
feature is incomplete but we wanna merge early to avoid a long-running
branch.

Release Notes:

- N/A

---------

Co-authored-by: Nathan <nathan@zed.dev>

crates/activity_indicator/src/activity_indicator.rs

@@ -107,6 +107,7 @@ impl ActivityIndicator {
                                 Editor::for_buffer(buffer, Some(project.clone()), cx)
                             })),
                             None,
+                            true,
                             cx,
                         );
                     })?;