fix(antigravity): retry excluded accounts via fallback LRU

[Ardem2025]

Summary

Builds on the family-scoped Antigravity lockout work in #5180 / release v3.8.39.

The combo same-model retry loop accumulates excluded Antigravity connection ids after account-level failures, but the auth selection path only treated excludeConnectionId !== null as a fallback scenario. Once retries accumulated exclusions through excludedConnectionIds, selection could fall back to normal sticky/priority behavior instead of LRU-selecting the next eligible account for the same model/family.

This patch treats any non-empty accumulated exclude set as fallback mode:

const isFallbackScenario = excludeConnectionId !== null || excludedConnectionIds.size > 0;

and adds safe telemetry for the retry decision:

• excluded_count
• redacted excluded account prefixes
• picked_lru
• candidate counts: active, excluded, modelLocked, familyLocked, eligible

It also keeps forced/pinned connectionId behavior unchanged: same-model account retry is still gated to Antigravity combo requests without a forced connection id.

While rebasing onto release/v3.8.39, the new test also caught that getQuotaScopeLabelForProvider(...) was referenced in src/sse/services/auth.ts without being imported. This branch includes the minimal import fix so the family-lockout path does not fail at runtime.

Test plan

• node --import tsx --import ./open-sse/utils/setupPolyfill.ts --import ./tests/_setup/isolateDataDir.ts --test tests/unit/auth-antigravity-account-retry-v2.test.ts
  • verifies accumulated multi-exclude enters fallback LRU and skips all excluded Antigravity accounts
  • verifies inferred Antigravity Gemini-family cooldown is ~30s when no upstream retry hint exists
• npx eslint src/sse/services/auth.ts tests/unit/auth-antigravity-account-retry-v2.test.ts
• import smoke: node --import tsx --import ./open-sse/utils/setupPolyfill.ts --eval "await import('./src/sse/services/auth.ts'); console.log('auth_import_ok')"
• npm run typecheck:core

[gemini-code-assist]

Code Review

This pull request enhances logging, tracking, and fallback logic for the 'antigravity' provider's connections, specifically handling Gemini family-level lockouts and cooldowns, and adds corresponding unit tests. The reviewer suggested simplifying the fallback scenario check in the round-robin strategy, pointing out that checking excludeConnectionId !== null is redundant since excludedConnectionIds already incorporates it.

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[gemini-code-assist]

Since excludedConnectionIds is constructed using normalizeExcludedConnectionIds(excludeConnectionId, options.excludeConnectionIds), it is guaranteed to already contain excludeConnectionId (if it is a valid non-empty string). Therefore, checking excludeConnectionId !== null is redundant when excludedConnectionIds.size > 0 is checked. We can simplify this expression to just excludedConnectionIds.size > 0.

Suggested change

	const isFallbackScenario = excludeConnectionId !== null || excludedConnectionIds.size > 0;
	const isFallbackScenario = excludedConnectionIds.size > 0;

[diegosouzapw]

Thanks @Ardem2025! Rebased onto the current release tip and merging. Two adjustments before merge (co-authored):

1. Strengthened the multi-exclude test into a real regression guard. The original v2 test excluded all-but-one account, so sticky and LRU both picked the survivor — it passed with or without the excludedConnectionIds.size > 0 fallback trigger. It now keeps two non-excluded accounts with diverging lastUsedAt, so it fails without the fallback change and passes with it (verified both ways via TDD).
2. Extracted the inferred 30s antigravity-family 429 base to a named constant with a note that real upstream Retry-After hints still win (they flow through exactCooldownMs / usedUpstreamRetryHint, not this base — confirmed the ?? ordering is correct).

The fallback LRU change correctly never re-selects excluded/terminal accounts (they're filtered out of orderedConnections upstream). Integrated into release/v3.8.40.