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/app-server/tests/suite/v2/rate_limits.rs

@@ -133,7 +133,10 @@ async fn get_account_rate_limits_returns_snapshot() -> Result<()> {
                     }
                 }
             }
-        ]
+        ],
+        "spend_control": {
+            "reached": true
+        }
     });
 
     Mock::given(method("GET"))
@@ -172,6 +175,7 @@ async fn get_account_rate_limits_returns_snapshot() -> Result<()> {
                 resets_at: Some(secondary_reset_timestamp),
             }),
             credits: None,
+            spend_control: Some(codex_app_server_protocol::SpendControlSnapshot { reached: true }),
             plan_type: Some(AccountPlanType::Pro),
         },
         rate_limits_by_limit_id: Some(
@@ -192,6 +196,9 @@ async fn get_account_rate_limits_returns_snapshot() -> Result<()> {
                             resets_at: Some(secondary_reset_timestamp),
                         }),
                         credits: None,
+                        spend_control: Some(codex_app_server_protocol::SpendControlSnapshot {
+                            reached: true,
+                        }),
                         plan_type: Some(AccountPlanType::Pro),
                     },
                 ),
@@ -207,6 +214,7 @@ async fn get_account_rate_limits_returns_snapshot() -> Result<()> {
                         }),
                         secondary: None,
                         credits: None,
+                        spend_control: None,
                         plan_type: Some(AccountPlanType::Pro),
                     },
                 ),