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/chatwidget.rs

@@ -423,6 +423,8 @@ mod status_controls;
 mod status_surfaces;
 mod streaming;
 use self::status_surfaces::CachedProjectRootName;
+mod thread_usage;
+pub(crate) use self::thread_usage::ThreadUsageOutcome;
 mod tokens;
 pub(crate) use self::tokens::TokenActivityView;
 mod tool_lifecycle;
@@ -764,6 +766,8 @@ pub(crate) struct ChatWidget {
     status_line_workspace_headline_last_requested_at: Option<Instant>,
     // Set after the backend reports the workspace-message feature gate is disabled.
     status_line_workspace_messages_disabled: bool,
+    // Cached backend-estimated cost and bounded refresh state for the current thread.
+    thread_usage: thread_usage::ThreadUsageState,
     // Current thread-goal status shown in the status line when plan mode is inactive.
     current_goal_status_indicator: Option<GoalStatusIndicator>,
     current_goal_status: Option<GoalStatusState>,