Add warning message when editing a message in a thread (#31508)

<img width="479" alt="Screenshot 2025-05-27 at 9 42 44 AM"
src="https://github.com/user-attachments/assets/7bd9e1b9-26b4-4396-9f93-e92a5f4ac2e1"
/>

Release Notes:

- Added notice that editing a message in the agent panel will restart
the thread from that point.

---------

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

crates/agent/src/active_thread.rs

@@ -2006,16 +2006,39 @@ impl ActiveThread {
                         .border_1()
                         .border_color(colors.border)
                         .hover(|hover| hover.border_color(colors.text_accent.opacity(0.5)))
-                        .cursor_pointer()
                         .child(
-                            h_flex()
+                            v_flex()
                                 .p_2p5()
                                 .gap_1()
-                                .items_end()
                                 .children(message_content)
                                 .when_some(editing_message_state, |this, state| {
                                     let focus_handle = state.editor.focus_handle(cx).clone();
-                                    this.w_full().justify_between().child(
+
+                                    this.child(
+                                        h_flex()
+                                            .w_full()
+                                            .gap_1()
+                                            .justify_between()
+                                            .flex_wrap()
+                                            .child(
+                                                h_flex()
+                                                    .gap_1p5()
+                                                    .child(
+                                                        div()
+                                                            .opacity(0.8)
+                                                            .child(
+                                                                Icon::new(IconName::Warning)
+                                                                    .size(IconSize::Indicator)
+                                                                    .color(Color::Warning)
+                                                            ),
+                                                    )
+                                                    .child(
+                                                        Label::new("Editing will restart the thread from this point.")
+                                                            .color(Color::Muted)
+                                                            .size(LabelSize::XSmall),
+                                                    ),
+                                            )
+                                            .child(
                                                 h_flex()
                                                     .gap_0p5()
                                                     .child(
@@ -2066,6 +2089,7 @@ impl ActiveThread {
                                                         ),
                                                     ),
                                             )
+                                    )
                                 }),
                         )
                         .on_click(cx.listener({