Option to Notify Workspace Owner When Usage Limit is Reached (#16969)

## Summary
- Replace the manual `/notify-owner` flow with an inline confirmation
prompt when a usage-based workspace member hits a credits-depleted
limit.
- Fetch the current workspace role from the live ChatGPT
`accounts/check/v4-2023-04-27` endpoint so owner/member behavior matches
the desktop and web clients.
- Keep owner, member, and spend-cap messaging distinct so we only offer
the owner nudge when the workspace is actually out of credits.

## What Changed
- `backend-client`
- Added a typed fetch for the current account role from
`accounts/check`.
  - Mapped backend role values into a Rust workspace-role enum.
- `app-server` and protocol
  - Added `workspaceRole` to `account/read` and `account/updated`.
- Derived `isWorkspaceOwner` from the live role, with a fallback to the
cached token claim when the role fetch is unavailable.
- `tui`
  - Removed the explicit `/notify-owner` slash command.
- When a member is blocked because the workspace is out of credits, the
error now prompts:
- `Your workspace is out of credits. Request more from your workspace
owner? [y/N]`
  - Choosing `y` sends the existing owner-notification request.
- Choosing `n`, pressing `Esc`, or accepting the default selection
dismisses the prompt without sending anything.
- Selection popups now honor explicit item shortcuts, which is how the
`y` / `n` interaction is wired.

## Reviewer Notes
- The main behavior change is scoped to usage-based workspace members
whose workspace credits are depleted.
- Spend-cap reached should not show the owner-notification prompt.
- Owners and admins should continue to see `/usage` guidance instead of
the member prompt.
- The live role fetch is best-effort; if it fails, we fall back to the
existing token-derived ownership signal.

## Testing
- Manual verification
  - Workspace owner does not see the member prompt.
- Workspace member with depleted credits sees the confirmation prompt
and can send the nudge with `y`.
- Workspace member with spend cap reached does not see the
owner-notification prompt.

### Workspace member out of usage

https://github.com/user-attachments/assets/341ac396-eff4-4a7f-bf0c-60660becbea1

### Workspace owner
<img width="1728" height="1086" alt="Screenshot 2026-04-09 at 11 48
22 AM"
src="https://github.com/user-attachments/assets/06262a45-e3fc-4cc4-8326-1cbedad46ed6"
/>

codex-rs/core/tests/suite/client.rs

@@ -2374,6 +2374,7 @@ async fn token_count_includes_rate_limits_snapshot() {
                     "resets_at": 1704074400
                 },
                 "credits": null,
+                "spend_control": null,
                 "plan_type": null
             }
         })
@@ -2425,6 +2426,7 @@ async fn token_count_includes_rate_limits_snapshot() {
                     "resets_at": 1704074400
                 },
                 "credits": null,
+                "spend_control": null,
                 "plan_type": null
             }
         })
@@ -2499,6 +2501,7 @@ async fn usage_limit_error_emits_rate_limit_event() -> anyhow::Result<()> {
             "resets_at": null
         },
         "credits": null,
+        "spend_control": null,
         "plan_type": null
     });
 

codex-rs/core/tests/suite/client_websockets.rs

@@ -1033,6 +1033,7 @@ async fn responses_websocket_usage_limit_error_emits_rate_limit_event() {
                     "resets_at": null
                 },
                 "credits": null,
+                "spend_control": null,
                 "plan_type": null
             }
         })