feat: allow esc to interrupt session (#2054)

## Summary
- allow Esc to interrupt the current session when a task is running
- document Esc as an interrupt key in status indicator

## Testing
- `just fmt`
- `just fix` *(fails: E0658 `let` expressions in this position are
unstable)*
- `cargo test --all-features` *(fails: E0658 `let` expressions in this
position are unstable)*

------
https://chatgpt.com/codex/tasks/task_i_689698cf605883208f57b0317ff6a303

codex-rs/tui/src/status_indicator_widget.rs

@@ -231,14 +231,14 @@ impl WidgetRef for StatusIndicatorWidget {
         spans.extend(animated_spans);
         // Space between header and bracket block
         spans.push(Span::raw(" "));
-        // Non-animated, dim bracket content, with only "Ctrl c" bold
+        // Non-animated, dim bracket content, with keys bold
         let bracket_prefix = format!("({elapsed}s • ");
         spans.push(Span::styled(
             bracket_prefix,
             Style::default().fg(Color::Gray).add_modifier(Modifier::DIM),
         ));
         spans.push(Span::styled(
-            "Ctrl C",
+            "Esc",
             Style::default()
                 .fg(Color::Gray)
                 .add_modifier(Modifier::DIM | Modifier::BOLD),