[WRONG BRANCH] feat(gui): mount generic OAuth pool settings on Antigravity accounts

[agentHits]

Summary

Stacked on lidge-jun#4560. Mounts the existing /api/pool/settings panel for Google Antigravity and other generic OAuth providers in the accounts workspace.

• The toggle writes providers.<name>.oauthAccountFailover.enabled (proactive pre-dispatch selection).
• Reactive 429 rotation is unchanged and stays presence-driven.
• quotaWindow remains Anthropic-only; generic saves omit it.
• The notice states that round-robin and fill-first are stored and apply when pool.kernel is on.

This does not add a Google-only router. It is the GUI remaining from lidge-jun#3375 / unification phase 5.

Verification

• cd gui && bun test tests/anthropic-pool-quota-window.test.tsx tests/generic-oauth-pool-settings.test.tsx tests/locale-parity.test.ts — 17 passed
• Focused oxlint on the touched panel files — no new findings besides a pre-existing react-compiler warning in ProviderAuthPanel.tsx

The new Account pool card mounts above the existing Antigravity account grid from lidge-jun#4560:

Checklist

• Scope stays focused and avoids unrelated cleanup.
• Docs or release notes were updated when needed.
• Security-sensitive changes were reviewed for secrets, auth, and unsafe defaults.

[github-actions]

✅ Deterministic PR hygiene checks passed.

[github-actions]

⏳ DRAFT

• wrong target branch (agentHits/antigravity); retarget to dev.

What to do

• Retarget this PR to dev — all contributions go to dev.

Its title has been prefixed with [WRONG BRANCH].
This pull request is being kept as a draft automatically. Once every issue above is resolved, it will be marked ready for review again.

[agentHits]

Closing this. It was opened on the fork against agentHits/antigravity, and the repo gate correctly marked it [WRONG BRANCH].

The GUI commit stays on agentHits/antigravity-pool-settings. After lidge-jun#4560 lands on dev, that one commit should be rebased onto dev and opened as a normal PR on lidge-jun/opencodex targeting dev.

The runtime slice is already on upstream: lidge-jun#4676