[codex] Match usage-limit TUI copy and owner nudge type

[richardopenai]

Summary

This PR is the second try at implementing an option for workspace members to notify their workspace owners when they run out of usage. Original PR: #16969

The original PR caused a sev because it introduced a new auth endpoint check that caused an infinite loop in Codex desktop. This PR does not add any additional auth checks and re-uses the existing endpoint - https://github.com/openai/openai/pull/820331

So this time around, this PR is much lower risk since it's just adding new UI when the user hits their rate limit and then sending a backend call to send the notification

• Use the existing RateLimitReachedType state in the TUI to select member/owner usage-limit copy instead of showing one generic workspace-credit prompt.
• Send AddCreditsNudgeCreditType::Credits for workspace member credit depletion and AddCreditsNudgeCreditType::UsageLimit for workspace member usage-limit requests.
• Track the in-flight owner nudge type so success, cooldown, and failure feedback use credits-specific or usage-limit-specific copy.
• Keep generic RateLimitReached and missing-state behavior unchanged.

Why

Desktop already distinguishes the two owner-nudge types:

• workspace member usage-limit increases use credit_type: "usage_limit"
• workspace member credit depletion uses credit_type: "credits"

The CLI already had the corresponding enum values, but the TUI prompt and completion feedback were not state-specific. This aligns the CLI with the data it already receives without adding endpoints, changing protocol shapes, or refactoring Desktop.

Testing

• cargo test -p codex-tui workspace_
• cargo test -p codex-tui status_
• cargo insta pending-snapshots -p codex-tui
• cargo insta accept -p codex-tui
• just fmt
• just fix -p codex-tui
• git diff --check

Desktop smoke

Ran the dev Desktop app from /Users/richardlee/code/openai/codex/codex-apps with CODEX_CLI_PATH=/Users/richardlee/code/codex/codex-rs/target/debug/codex.

Member account richardlee+member@mail.openai.com:

• Desktop showed the usage-limit card with Usage limit reached, Request a limit increase from your owner to continue using codex., and Request Increase.
• Clicking the CTA showed the usage-specific cooldown toast: A limit increase was already requested recently.
• Re-click/network monitoring did not show repeated nudge requests.

Owner account richardlee+dogfood@mail.openai.com:

• After switching the dev app to GPT-5.4, Desktop showed owner-only limit UI: Usage limit reached, You've reached your usage limit. Increase your limits to continue using codex., and Increase Spend Cap.
• No owner-nudge CTA was present for the owner state.
• App-server logs showed the expected turn lifecycle and one account/rateLimits/updated, with no repeated request loop.

CLI smoke:

• Member CLI followed the existing /api/codex/usage state, which currently returns workspace_member_credits_depleted for the dogfood member account. That produced the credits prompt as designed from the CLI state source, while Desktop's failed turn showed usage-limit UI.
• Owner CLI with the owner account showed You're out of credits. Your workspace is out of credits. Add credits to continue using Codex. and did not show an owner-nudge prompt.

Note

The live dogfood member account currently has a backend state mismatch between /api/codex/usage and the Desktop turn-failure UI. This PR intentionally does not infer state from other fields; it uses the existing CLI RateLimitReachedType as requested.