Update interruption error message styling (#3470)

<img width="497" height="76" alt="image"
src="https://github.com/user-attachments/assets/a1ad279d-1d01-41cd-ac14-b3343a392563"
/>

<img width="493" height="74" alt="image"
src="https://github.com/user-attachments/assets/baf487ba-430e-40fe-8944-2071ec052962"
/>

codex-rs/tui/src/chatwidget.rs

@@ -289,7 +289,9 @@ impl ChatWidget {
     /// separated by newlines rather than auto‑submitting the next one.
     fn on_interrupted_turn(&mut self) {
         // Finalize, log a gentle prompt, and clear running state.
-        self.finalize_turn_with_error_message("Tell the model what to do differently".to_owned());
+        self.finalize_turn_with_error_message(
+            "Conversation interrupted - tell the model what to do differently".to_owned(),
+        );
 
         // If any messages were queued during the task, restore them into the composer.
         if !self.queued_user_messages.is_empty() {

codex-rs/tui/src/chatwidget/snapshots/codex_tui__chatwidget__tests__disabled_slash_command_while_task_running_snapshot.snap

@@ -2,4 +2,4 @@
 source: tui/src/chatwidget/tests.rs
 expression: blob
 ---
-🖐  '/model' is disabled while a task is in progress.
+■ '/model' is disabled while a task is in progress.

codex-rs/tui/src/history_cell.rs

@@ -1063,8 +1063,7 @@ pub(crate) fn new_error_event(message: String) -> PlainHistoryCell {
     // Use a hair space (U+200A) to create a subtle, near-invisible separation
     // before the text. VS16 is intentionally omitted to keep spacing tighter
     // in terminals like Ghostty.
-    let lines: Vec<Line<'static>> =
-        vec![vec![padded_emoji("🖐").red().bold(), " ".into(), message.into()].into()];
+    let lines: Vec<Line<'static>> = vec![vec![format!("■ {message}").red()].into()];
     PlainHistoryCell { lines }
 }