fix emoji spacing (#2735)

before:
<img width="295" height="266" alt="Screenshot 2025-08-26 at 5 05 03 PM"
src="https://github.com/user-attachments/assets/3e876f08-26d0-407e-a995-28fd072e288f"
/>

after:
<img width="295" height="129" alt="Screenshot 2025-08-26 at 5 05 30 PM"
src="https://github.com/user-attachments/assets/2a019d52-19ed-40ef-8155-4f02c400796a"
/>

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

@@ -3,4 +3,4 @@ source: tui/src/chatwidget/tests.rs
 expression: exec_blob
 ---
 >_
-  ✗ ⌨️  sleep 1
+  ✗ ⌨️ sleep 1

codex-rs/tui/src/chatwidget/tests.rs

@@ -1246,7 +1246,7 @@ fn stream_error_is_rendered_to_history() {
     let cells = drain_insert_history(&mut rx);
     assert!(!cells.is_empty(), "expected a history cell for StreamError");
     let blob = lines_to_single_string(cells.last().unwrap());
-    assert!(blob.contains("⚠  "));
+    assert!(blob.contains("⚠\u{200A} "));
     assert!(blob.contains("stream error:"));
     assert!(blob.contains("idle timeout waiting for SSE"));
 }

codex-rs/tui/src/history_cell.rs

@@ -230,14 +230,11 @@ fn pretty_provider_name(id: &str) -> String {
         title_case(id)
     }
 }
-/// Return the emoji followed by a hair space (U+200A) and a normal space.
-/// This creates a reasonable gap across different terminals,
-/// in particular Terminal.app and iTerm, which render too tightly with just a single normal space.
-///
-/// Improvements here could be to condition this behavior on terminal,
-/// or possibly on emoji.
+/// Return the emoji followed by a hair space (U+200A).
+/// Using only the hair space avoids excessive padding after the emoji while
+/// still providing a small visual gap across terminals.
 fn padded_emoji(emoji: &str) -> String {
-    format!("{emoji}\u{200A} ")
+    format!("{emoji}\u{200A}")
 }
 
 /// Convenience function over `padded_emoji()`.
@@ -900,14 +897,19 @@ pub(crate) fn new_error_event(message: String) -> PlainHistoryCell {
     // in terminals like Ghostty.
     let lines: Vec<Line<'static>> = vec![
         "".into(),
-        vec![padded_emoji("🖐").red().bold(), message.into()].into(),
+        vec![padded_emoji("🖐").red().bold(), " ".into(), message.into()].into(),
     ];
     PlainHistoryCell { lines }
 }
 
 pub(crate) fn new_stream_error_event(message: String) -> PlainHistoryCell {
     let lines: Vec<Line<'static>> = vec![
-        vec![padded_emoji("⚠").magenta().bold(), message.dim()].into(),
+        vec![
+            padded_emoji("⚠").magenta().bold(),
+            " ".into(),
+            message.dim(),
+        ]
+        .into(),
         "".into(),
     ];
     PlainHistoryCell { lines }