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/app-server-protocol/src/export.rs

@@ -2145,6 +2145,17 @@ mod tests {
             client_request_ts.contains("MockExperimentalMethodParams"),
             false
         );
+        const LEGACY_ACCOUNT_USAGE_REQUEST: &str = concat!(
+            "{ \"method\": \"account/usage/read\", id: RequestId, ",
+            "params?: GetAccountTokenUsageParams | undefined, }"
+        );
+        assert!(client_request_ts.contains(LEGACY_ACCOUNT_USAGE_REQUEST));
+        let account_usage_response_ts = std::str::from_utf8(
+            fixture_tree
+                .get(Path::new("v2/GetAccountTokenUsageResponse.ts"))
+                .ok_or_else(|| anyhow::anyhow!("missing account usage response fixture"))?,
+        )?;
+        assert!(account_usage_response_ts.contains("threadUsage?: ThreadUsage | null"));
         let server_request_ts = std::str::from_utf8(
             fixture_tree
                 .get(Path::new("ServerRequest.ts"))
@@ -2217,7 +2228,12 @@ mod tests {
                 });
 
             let contents = std::str::from_utf8(contents)?;
-            if contents.contains("| undefined") {
+            // The stable usage RPC originally required `params: undefined`. Keep that exact
+            // legacy value accepted while extending the same method with optional thread params.
+            let legacy_account_usage_undefined = path == Path::new("ClientRequest.ts")
+                && contents.matches("| undefined").count() == 1
+                && contents.contains(LEGACY_ACCOUNT_USAGE_REQUEST);
+            if contents.contains("| undefined") && !legacy_account_usage_undefined {
                 undefined_offenders.push(path.clone());
             }
 
@@ -2329,9 +2345,14 @@ mod tests {
 
                 // If the last non-whitespace before ':' is '?', then this is an
                 // optional field with a nullable type (i.e., "?: T | null").
-                // These are only allowed in *Params types.
+                // These are only allowed in *Params types, except the additive stable usage
+                // response field, which older servers omit and newer servers return as null.
+                let legacy_account_usage_response = path
+                    == Path::new("v2/GetAccountTokenUsageResponse.ts")
+                    && field_prefix.trim() == "threadUsage?";
                 if field_prefix.chars().rev().find(|c| !c.is_whitespace()) == Some('?')
                     && !allow_optional_nullable
+                    && !legacy_account_usage_response
                 {
                     let line_number =
                         contents[..abs_idx].chars().filter(|c| *c == '\n').count() + 1;