update composer + user message styling (#4240)

Changes:

- the composer and user messages now have a colored background that
stretches the entire width of the terminal.
- the prompt character was changed from a cyan `▌` to a bold `›`.
- the "working" shimmer now follows the "dark gray" color of the
terminal, better matching the terminal's color scheme

| Terminal + Background        | Screenshot |
|------------------------------|------------|
| iTerm with dark bg | <img width="810" height="641" alt="Screenshot
2025-09-25 at 11 44 52 AM"
src="https://github.com/user-attachments/assets/1317e579-64a9-4785-93e6-98b0258f5d92"
/> |
| iTerm with light bg | <img width="845" height="540" alt="Screenshot
2025-09-25 at 11 46 29 AM"
src="https://github.com/user-attachments/assets/e671d490-c747-4460-af0b-3f8d7f7a6b8e"
/> |
| iTerm with color bg | <img width="825" height="564" alt="Screenshot
2025-09-25 at 11 47 12 AM"
src="https://github.com/user-attachments/assets/141cda1b-1164-41d5-87da-3be11e6a3063"
/> |
| Terminal.app with dark bg | <img width="577" height="367"
alt="Screenshot 2025-09-25 at 11 45 22 AM"
src="https://github.com/user-attachments/assets/93fc4781-99f7-4ee7-9c8e-3db3cd854fe5"
/> |
| Terminal.app with light bg | <img width="577" height="367"
alt="Screenshot 2025-09-25 at 11 46 04 AM"
src="https://github.com/user-attachments/assets/19bf6a3c-91e0-447b-9667-b8033f512219"
/> |
| Terminal.app with color bg | <img width="577" height="367"
alt="Screenshot 2025-09-25 at 11 45 50 AM"
src="https://github.com/user-attachments/assets/dd7c4b5b-342e-4028-8140-f4e65752bd0b"
/> |

codex-rs/tui/src/chatwidget.rs

@@ -59,6 +59,7 @@ use tracing::debug;
 
 use crate::app_event::AppEvent;
 use crate::app_event_sender::AppEventSender;
+use crate::bottom_pane::ApprovalRequest;
 use crate::bottom_pane::BottomPane;
 use crate::bottom_pane::BottomPaneParams;
 use crate::bottom_pane::CancellationEvent;
@@ -79,13 +80,11 @@ use crate::history_cell::AgentMessageCell;
 use crate::history_cell::HistoryCell;
 use crate::history_cell::McpToolCallCell;
 use crate::history_cell::PatchEventType;
-use crate::history_cell::RateLimitSnapshotDisplay;
 use crate::markdown::append_markdown;
 use crate::slash_command::SlashCommand;
+use crate::status::RateLimitSnapshotDisplay;
 use crate::text_formatting::truncate_text;
 use crate::tui::FrameRequester;
-// streaming internals are provided by crate::streaming and crate::markdown_stream
-use crate::bottom_pane::ApprovalRequest;
 mod interrupts;
 use self::interrupts::InterruptManager;
 mod agent;
@@ -417,7 +416,7 @@ impl ChatWidget {
                     .and_then(|window| window.window_minutes),
             );
 
-            let display = history_cell::rate_limit_snapshot_display(&snapshot, Local::now());
+            let display = crate::status::rate_limit_snapshot_display(&snapshot, Local::now());
             self.rate_limit_snapshot = Some(display);
 
             if !warnings.is_empty() {
@@ -1542,7 +1541,7 @@ impl ChatWidget {
             default_usage = TokenUsage::default();
             &default_usage
         };
-        self.add_to_history(history_cell::new_status_output(
+        self.add_to_history(crate::status::new_status_output(
             &self.config,
             usage_ref,
             &self.conversation_id,