Format large numbers in a more readable way. (#2046)

- In the bottom line of the TUI, print the number of tokens to 3 sigfigs
  with an SI suffix, e.g. "1.23K".
- Elsewhere where we print a number, I figure it's worthwhile to print
  the exact number, because e.g. it's a summary of your session. Here we print
  the numbers comma-separated.

codex-rs/tui/src/bottom_pane/chat_composer.rs

@@ -1,4 +1,5 @@
 use codex_core::protocol::TokenUsageInfo;
+use codex_protocol::num_format::format_si_suffix;
 use crossterm::event::KeyCode;
 use crossterm::event::KeyEvent;
 use crossterm::event::KeyEventKind;
@@ -1276,8 +1277,11 @@ impl WidgetRef for ChatComposer {
                     let token_usage = &token_usage_info.total_token_usage;
                     hint.push("   ".into());
                     hint.push(
-                        Span::from(format!("{} tokens used", token_usage.blended_total()))
-                            .style(Style::default().add_modifier(Modifier::DIM)),
+                        Span::from(format!(
+                            "{} tokens used",
+                            format_si_suffix(token_usage.blended_total())
+                        ))
+                        .style(Style::default().add_modifier(Modifier::DIM)),
                     );
                     let last_token_usage = &token_usage_info.last_token_usage;
                     if let Some(context_window) = token_usage_info.model_context_window {

codex-rs/tui/src/history_cell.rs

@@ -28,6 +28,7 @@ use codex_core::protocol::SandboxPolicy;
 use codex_core::protocol::SessionConfiguredEvent;
 use codex_core::protocol::TokenUsage;
 use codex_protocol::mcp_protocol::ConversationId;
+use codex_protocol::num_format::format_with_separators;
 use codex_protocol::parse_command::ParsedCommand;
 use image::DynamicImage;
 use image::ImageReader;
@@ -964,7 +965,7 @@ pub(crate) fn new_status_output(
     // Input: <input> [+ <cached> cached]
     let mut input_line_spans: Vec<Span<'static>> = vec![
         "  • Input: ".into(),
-        usage.non_cached_input().to_string().into(),
+        format_with_separators(usage.non_cached_input()).into(),
     ];
     if usage.cached_input_tokens > 0 {
         let cached = usage.cached_input_tokens;
@@ -974,12 +975,12 @@ pub(crate) fn new_status_output(
     // Output: <output>
     lines.push(Line::from(vec![
         "  • Output: ".into(),
-        usage.output_tokens.to_string().into(),
+        format_with_separators(usage.output_tokens).into(),
     ]));
     // Total: <total>
     lines.push(Line::from(vec![
         "  • Total: ".into(),
-        usage.blended_total().to_string().into(),
+        format_with_separators(usage.blended_total()).into(),
     ]));
 
     PlainHistoryCell { lines }