acp thread view: Floating editing message controls (#36283)

Prevents layout shift when focusing the editor

Release Notes:

- N/A

---------

Co-authored-by: Danilo Leal <daniloleal09@gmail.com>

crates/agent_ui/src/acp/entry_view_state.rs

@@ -67,6 +67,7 @@ impl EntryViewState {
                         self.project.clone(),
                         self.thread_store.clone(),
                         self.text_thread_store.clone(),
+                        "Edit message － @ to include context",
                         editor::EditorMode::AutoHeight {
                             min_lines: 1,
                             max_lines: None,