Show estimated thread usage in /status (#38281)

## What changed

- Extend `account/usage/read` with an optional `threadId` request and a
  backward-compatible `threadUsage` response containing estimated credits,
  optional USD cost, and model, reasoning, speed, and token breakdowns.
- Fetch thread usage for eligible Business and Enterprise plans when `/status`
  is opened, then update the rendered status card asynchronously.
- Preserve terminal scrollback when replacing a visible status-card tail, and
  append a refreshed card when the original tail can no longer be updated.

## Testing

- Add app-server coverage for authentication, canonical thread IDs,
  unavailable billing routes, and malformed IDs.
- Add TUI coverage for usage formatting, stale responses, retries, history
  updates, terminal reflow, and scrollback preservation.

GitOrigin-RevId: 49300914b3fba917c0f08e8595363e04e5ba6d37

codex-rs/tui/src/app/event_dispatch.rs

@@ -983,6 +983,12 @@ impl App {
             AppEvent::RefreshTokenActivity { request_id } => {
                 self.refresh_token_activity(app_server, request_id);
             }
+            AppEvent::RefreshThreadUsage {
+                thread_id,
+                request_id,
+            } => {
+                self.refresh_thread_usage(app_server, thread_id, request_id);
+            }
             AppEvent::RefreshStatusLineWorkspaceHeadline { request_id } => {
                 self.refresh_status_line_workspace_headline(app_server, request_id);
             }
@@ -1208,6 +1214,13 @@ impl App {
                     self.insert_pending_usage_output_if_ready(tui);
                 }
             }
+            AppEvent::ThreadUsageLoaded {
+                thread_id,
+                request_id,
+                result,
+            } => {
+                self.finish_thread_usage_refresh(tui, thread_id, request_id, result)?;
+            }
             AppEvent::CommitPendingUsageOutput => {
                 self.insert_pending_usage_output_if_ready(tui);
             }