fix(antigravity): implement quota cooldown family lock and retry limits

[Ardem2025]

Changes:

1. Added antigravity per-family models cooldown and locking logic (antigravityQuotaResetCooldownMs / isAntigravityScopeUnavailable).
2. Prevent global account lock on 429 errors from antigravity requests by locking key-specific family models instead, checking quota cache reset intervals.
3. Added full unit tests mapping different test cases including 499 (user cancelation behavior) and 429 cooldowns.
4. Fixed issue where gemini/claude specific model groups would not fallback correctly under concurrent stress.

[diegosouzapw]

Thanks for this — the family-lock idea here is the starting point that you kept iterating on
in #6680 and eventually #10011, which we're planning to merge as the final, most complete
version (dedicated lease/routing modules, tests passing on the current release branch).
Closing this one in favor of your own later work rather than asking you to rebase an
intermediate version.

Triage note: this is the review recommendation — the close itself happens only after the maintainer's per-PR sign-off (and, where a superseding PR is named, after it has landed). Nothing is being closed by this comment.

[diegosouzapw]

Closing the second link of your own chain — #6064 (03/07) → #6281 (05/07) → #6680 (08/07) → #10011 (10/08).

This PR extends antigravityQuotaResetCooldownMs, the function #6064 introduced two days earlier, and adds isAntigravityScopeUnavailable on top (+245/-171 in src/sse/services/auth.ts over #6064). Three days later #6680 grew the same two files by another +185/-42, and #10011 then moved the whole approach out of auth.ts into dedicated modules.

All four are closed now for the same reason, explained in full on #10011: the release branch settled the family-vs-model quota question with selectAntigravityQuotaWindowNames (aggregate family windows in open-sse/services/antigravityQuotaFamily.ts), a different design from the per-family cooldown persisted here. This branch has been CONFLICTING against main since 5 July.

The account-lease idea from your last iteration is being carried forward as a fresh PR credited to you — see #10011. Thanks, @Ardem2025.