Inline terminal assistant v2 (#21888)

Follow-up to https://github.com/zed-industries/zed/pull/21828 to add it
to the terminal as well.


https://github.com/user-attachments/assets/505d1443-4081-4dd8-9725-17d85532f52d

As with the previous PR, there's plenty of code duplication here; the
plan is to do more code sharing in separate PRs!


Release Notes:

- N/A

crates/assistant2/src/assistant.rs

@@ -7,6 +7,7 @@ mod inline_assistant;
 mod message_editor;
 mod prompts;
 mod streaming_diff;
+mod terminal_inline_assistant;
 mod thread;
 mod thread_history;
 mod thread_store;
@@ -63,6 +64,12 @@ pub fn init(fs: Arc<dyn Fs>, client: Arc<Client>, stdout_is_a_pty: bool, cx: &mu
         client.telemetry().clone(),
         cx,
     );
+    terminal_inline_assistant::init(
+        fs.clone(),
+        prompt_builder.clone(),
+        client.telemetry().clone(),
+        cx,
+    );
 
     feature_gate_assistant2_actions(cx);
 }