Adds end-to-end support for Google One AI credits in quota exhaustion flows:
- New billing module (packages/core/src/billing/) with credit balance
checking, overage strategy management, and G1 URL construction
- OverageMenuDialog and EmptyWalletDialog UI components for quota
exhaustion with credit purchase options
- Credits flow handler extracted to creditsFlowHandler.ts with overage
menu, empty wallet, and auto-use-credits logic
- Server-side credit tracking: enabledCreditTypes on requests,
consumed/remaining credits from streaming responses
- Billing telemetry events (overage menu shown, option selected, credits
used, credit purchase click, API key updated)
- OpenTelemetry metrics for overage option and credit purchase counters
- Credit balance display in /stats command with refresh support
- Settings: general.overageStrategy (ask/always/never) for credit usage
- Error handling: INSUFFICIENT_G1_CREDITS_BALANCE as terminal error
regardless of domain field presence
- Persistent info message after
Gaurav Ghosh