sum_tree: Replace rayon with futures (#41586)

Release Notes:

- N/A *or* Added/Fixed/Improved ...

Co-authored by: Kate <kate@zed.dev>

crates/agent_ui/src/agent_configuration.rs

@@ -28,6 +28,7 @@ use project::{
     agent_server_store::{AgentServerStore, CLAUDE_CODE_NAME, CODEX_NAME, GEMINI_NAME},
     context_server_store::{ContextServerConfiguration, ContextServerStatus, ContextServerStore},
 };
+use rope::Rope;
 use settings::{SettingsStore, update_settings_file};
 use ui::{
     Chip, CommonAnimationExt, ContextMenu, Disclosure, Divider, DividerColor, ElevationIndex,
@@ -1114,8 +1115,11 @@ async fn open_new_agent_servers_entry_in_settings_editor(
 ) -> Result<()> {
     let settings_editor = workspace
         .update_in(cx, |_, window, cx| {
-            create_and_open_local_file(paths::settings_file(), window, cx, || {
-                settings::initial_user_settings_content().as_ref().into()
+            create_and_open_local_file(paths::settings_file(), window, cx, |cx| {
+                Rope::from_str(
+                    &settings::initial_user_settings_content(),
+                    cx.background_executor(),
+                )
             })
         })?
         .await?

crates/agent_ui/src/buffer_codegen.rs

@@ -487,9 +487,10 @@ impl CodegenAlternative {
     ) {
         let start_time = Instant::now();
         let snapshot = self.snapshot.clone();
-        let selected_text = snapshot
-            .text_for_range(self.range.start..self.range.end)
-            .collect::<Rope>();
+        let selected_text = Rope::from_iter(
+            snapshot.text_for_range(self.range.start..self.range.end),
+            cx.background_executor(),
+        );
 
         let selection_start = self.range.start.to_point(&snapshot);