Dedupe PromptBuilder construction (#23496)

This PR dedupes the construction of the `PromptBuilder`.

Previously this was constructed by both `assistant` and `assistant2`,
but now we construct it outside and pass it in.

Release Notes:

- N/A

crates/zed/src/main.rs

@@ -25,6 +25,7 @@ use gpui::{
 use http_client::{read_proxy_from_env, Uri};
 use language::LanguageRegistry;
 use log::LevelFilter;
+use prompt_library::PromptBuilder;
 use reqwest_client::ReqwestClient;
 
 use assets::Assets;
@@ -443,16 +444,17 @@ fn main() {
             app_state.user_store.clone(),
             cx,
         );
-        let prompt_builder = assistant::init(
+        let prompt_builder = PromptBuilder::load(app_state.fs.clone(), stdout_is_a_pty(), cx);
+        assistant::init(
             app_state.fs.clone(),
             app_state.client.clone(),
-            stdout_is_a_pty(),
+            prompt_builder.clone(),
             cx,
         );
         assistant2::init(
             app_state.fs.clone(),
             app_state.client.clone(),
-            stdout_is_a_pty(),
+            prompt_builder.clone(),
             cx,
         );
         assistant_tools::init(cx);

crates/zed/src/zed.rs

@@ -3833,8 +3833,13 @@ mod tests {
                 app_state.fs.clone(),
                 cx,
             );
-            let prompt_builder =
-                assistant::init(app_state.fs.clone(), app_state.client.clone(), false, cx);
+            let prompt_builder = PromptBuilder::load(app_state.fs.clone(), false, cx);
+            assistant::init(
+                app_state.fs.clone(),
+                app_state.client.clone(),
+                prompt_builder.clone(),
+                cx,
+            );
             repl::init(app_state.fs.clone(), cx);
             repl::notebook::init(cx);
             tasks_ui::init(cx);