Round out the credit-notice handling from the previous commit with the two
optional pieces from the issue:
- Native OS notification for the urgent pair. `credits.depleted` /
`credits.restored` also fire an Electron notification when Hermes is
backgrounded, via a new `credits` NativeNotificationKind (the existing
five didn't fit) with its own toggle in Settings → Notifications (the
panel is data-driven off NATIVE_NOTIFICATION_KINDS, so the toggle and
i18n are the only additions). The escalating usage line and grant-spent
notice stay in-app toasts only. Dispatch is `global` (account-wide, not
session-bound) and gated by the user's prefs + backgrounded check.
- Billing-page nudge. A `credits.*` crossing invalidates the
`['billing','state']` query so Settings → Billing reflects the change
immediately instead of waiting up to 30s for its poll.
`nativeNoticeInput()` is a pure mapping (urgent-key gate → native input),
unit-tested directly; the gateway-event branch does the localized-title
lookup and gated dispatch. i18n added for all four locales.
b8a2b9b93e