fix(tui): reduce startup and new-session latency (#17039)

## TL;DR

- Fetches account/rateLimits/read asynchronously so the TUI can continue
starting without waiting for the rate-limit response.
- Fixes the /status card so it no longer leaves a stale “refreshing
cached limits...” notice in terminal history.

## Problem

The TUI bootstrap path fetched account rate limits synchronously
(`account/rateLimits/read`) before the event loop started for
ChatGPT/OpenAI-authenticated startups. This added ~670 ms of blocking
latency in the measured hot-start case, even though rate-limit data is
not needed to render the initial UI or accept user input. The delay was
especially noticeable on hot starts where every other RPC
(`account/read`, `model/list`, `thread/start`) completed in under 70 ms
total.

Moving that fetch to the background also exposed a `/status` UI bug: the
status card is flattened into terminal scrollback when it is inserted. A
transient "refreshing limits in background..." line could not be cleared
later, because the async completion updated the retained `HistoryCell`,
not the already-written terminal history.

## Mental model

Before this change, `AppServerSession::bootstrap()` performed three
sequential RPCs: `account/read` → `model/list` →
`account/rateLimits/read`. The result of the third call was baked into
`AppServerBootstrap` and applied to the chat widget before the event
loop began.

After this change, `bootstrap()` only performs two RPCs (`account/read`
+ `model/list`), and rate-limit fetching is kicked off as an async
background task immediately after the first frame is scheduled. A new
enum, `RateLimitRefreshOrigin`, tags each fetch so the event handler
knows whether the result came from the startup prefetch or from a
user-initiated `/status` command; they have different completion
side-effects.

The `get_login_status()` helper (used outside the main app flow) was
also decoupled: it previously called the full `bootstrap()` just to
check auth mode, wasting model-list and rate-limit work. It now calls
the narrower `read_account()` directly.

For `/status`, this PR keeps the background refresh request but stops
printing transient refresh notices into status history when cached
limits are already available. If a refresh updates the cache, the next
`/status` command will render the new values.

## Non-goals

- This change does not alter the rate-limit data itself.
- This change does not introduce caching, retries, or staleness
management for rate limits.
- This change does not affect the `model/list` or `thread/start` RPCs;
they remain on the critical startup path.

## Tradeoffs

- **Stale-on-first-render**: The status bar will briefly show no
rate-limit info until the background fetch completes; observed
background fetches landed roughly in the 400-900 ms range after the UI
appeared. This is acceptable because the user cannot meaningfully act on
rate-limit data in the first fraction of a second.
- **Error silence on startup prefetch**: If the startup prefetch fails,
the error is logged but the UI is not notified (unlike `/status` refresh
failures, which go through the status-command completion path). This
avoids surfacing transient network errors as a startup blocker.
- **Static `/status` history**: `/status` output is terminal history,
not a live widget. The card now avoids progress-style language that
would appear stuck in scrollback; users can run `/status` again to see
newly cached values.
- **`account_auth_mode` field removed from `AppServerBootstrap`**: The
only consumer was `get_login_status()`, which no longer goes through
`bootstrap()`. The field was dead weight.

## Architecture

### New types

- `RateLimitRefreshOrigin` (in `app_event.rs`): A `Copy` enum
distinguishing `StartupPrefetch` from `StatusCommand { request_id }`.
Carried through `RefreshRateLimits` and `RateLimitsLoaded` events so the
handler applies the right completion behavior.

### Modified types

- `AppServerBootstrap`: Lost `account_auth_mode` and
`rate_limit_snapshots`; gained `requires_openai_auth: bool` (passed
through from the account response so the caller can decide whether to
fire the prefetch).

### Control flow

1. `bootstrap()` returns with `requires_openai_auth` and
`has_chatgpt_account`.
2. After scheduling the first frame, `App::run_inner` fires
`refresh_rate_limits(StartupPrefetch)` if both flags are true.
3. When `RateLimitsLoaded { StartupPrefetch, Ok(..) }` arrives,
snapshots are applied and a frame is scheduled to repaint the status
bar.
4. When `RateLimitsLoaded { StartupPrefetch, Err(..) }` arrives, the
error is logged and no UI update occurs.
5. `/status`-initiated refreshes continue to use `StatusCommand {
request_id }` and call `finish_status_rate_limit_refresh` on completion
(success or failure).
6. `/status` history cells with cached rate-limit rows no longer render
an additional "refreshing limits" notice; the async refresh updates the
cache for future status output.

### Extracted method

- `AppServerSession::read_account()`: Factored out of `bootstrap()` so
that `get_login_status()` can call it independently without triggering
model-list or rate-limit work.

## Observability

- The existing `tracing::warn!` for rate-limit fetch failures is
preserved for the startup path.
- No new metrics or spans are introduced. The startup-time improvement
is observable via the existing `ready` timestamp in TUI startup logs.

## Tests

- Existing tests in `status_command_tests.rs` are updated to match on
`RateLimitRefreshOrigin::StatusCommand { request_id }` instead of a bare
`request_id`.
- Focused `/status` tests now assert that status history avoids
transient refresh text, continues to request an async refresh, and uses
refreshed cached limits in future status output.
- No new tests are added for the startup prefetch path because it is a
fire-and-forget spawn with no observable side-effect other than the
widget state update, which is already covered by the
snapshot-application tests.

---------

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

codex-rs/tui/src/lib.rs

@@ -1615,6 +1615,9 @@ pub enum LoginStatus {
     NotAuthenticated,
 }
 
+/// Determines the user's authentication mode using a lightweight account read
+/// rather than a full `bootstrap`, avoiding the model-list fetch and
+/// rate-limit round-trip that `bootstrap` would trigger.
 async fn get_login_status(
     app_server: &mut AppServerSession,
     config: &Config,
@@ -1623,9 +1626,14 @@ async fn get_login_status(
         return Ok(LoginStatus::NotAuthenticated);
     }
 
-    let bootstrap = app_server.bootstrap(config).await?;
-    Ok(match bootstrap.account_auth_mode {
-        Some(auth_mode) => LoginStatus::AuthMode(auth_mode),
+    let account = app_server.read_account().await?;
+    Ok(match account.account {
+        Some(codex_app_server_protocol::Account::ApiKey {}) => {
+            LoginStatus::AuthMode(AppServerAuthMode::ApiKey)
+        }
+        Some(codex_app_server_protocol::Account::Chatgpt { .. }) => {
+            LoginStatus::AuthMode(AppServerAuthMode::Chatgpt)
+        }
         None => LoginStatus::NotAuthenticated,
     })
 }